[APM Go] fix and clarify dd-trace-go v2 docs for release

[hannahkm]

What does this PR do? What is the motivation?

To minimize confusion with the differences between v1 and v2, we clarify when there are not significant changes to the specific product and link customers to the migration guide whenever possible.

Also see profiling changes here.

• Add reusable snippet to link users to migration guide. This will ease maintenance burden too.
• Swap order of v1 and v2 tabs--put v2 first.
• Remove mention of v2 in Preview.
• Add GA date to support table (subject to change).
• Refine migration guide to include more context. Preview
• TODO: Swap v2 code statements to come first OR remove v1 import statements entirely.

Merge instructions

Merge whenever possible, preferably before or around the dd-trace-go v2 GA release.

Merge readiness:

• Ready for merge

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Additional notes

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/containers/amazon_ecs/apm
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/containers/docker/apm
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/data_streams/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/database_monitoring/connect_dbm_and_apm
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/opentelemetry/instrument/instrumentation_libraries
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/profiler/enabling/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/profiler/guide/isolate-outliers-in-monolithic-services
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/security/application_security/threats/add-user-info
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/security/application_security/threats/setup/compatibility/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/security/application_security/threats/setup/threat_detection/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/security/application_security/troubleshooting
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/security/code_security/software_composition_analysis/setup_runtime/compatibility/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/aws_lambda/installation/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/azure_app_services/azure_app_services_container
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/azure_container_apps/
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/google_cloud_run/
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/google_cloud_run/functions
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/serverless/guide/datadog_forwarder_go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/faq/trace_sampling_and_storage
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/guide/instrument_custom_method
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/guide/tutorial-enable-go-aws-ecs-ec2
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/guide/tutorial-enable-go-aws-ecs-fargate
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/guide/tutorial-enable-go-containers
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/guide/tutorial-enable-go-host
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/legacy_app_analytics/
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/metrics/runtime_metrics/
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/other_telemetry/connect_logs_and_traces/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/automatic_instrumentation/dd_libraries/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/compatibility/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/custom_instrumentation/go/dd-api
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/custom_instrumentation/go/migration
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/custom_instrumentation/go/otel
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_collection/library_config/go
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/trace_pipeline/ingestion_mechanisms
• https://docs-staging.datadoghq.com/hannahkm/clarify-v2-docs/tracing/troubleshooting/tracer_debug_logs

[hannahkm]

Most important to review here is whether statements left under DSM and OTel files are accurate; has v2 made significant changes to their APIs? I don't think it has, but I'd like to confirm this.

[felixge]

Thanks for working on this 🙇 . I left some comments. But since this is still draft, I'm not sure if I should try to do a complete review at this point? LMK

[felixge]

Did we have a good reason for making this change? If yes, maybe we can communicate it here?

Edit: On second thought, did we even really make this change 🤔? Looking at the v2-dev branch, it doesn't seem to be the case?

[hannahkm]

Looks like a typo! I think it should be that functions previously in ddtrace are now in ddtrace/tracer. Thanks!

[hannahkm]

It also looks like the examples were incorrect. @darccio I updated them to be more representative, but let me know if there's a more concise/better example of the ddtrace --> ddtrace/tracer change?

[hannahkm]

@felixge Thank you for the eyes! Might as well make this PR open to review. 🏁