Fix getProxies to reflect changes in GatewayD v0.9.7+

[mostafa]

Ticket(s)

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Description

This PR aims to update the getProxies function to pick up the latest change in GatewayD, which is the addition of config blocks for multi-proxy and load-balancing scenarios. Now the plugin uses gRPC to retrieve the list of proxies instead of HTTP.

Important

These changes are compatible with GatewayD v0.9.7+ and backward-incompatible with previous versions of GatewayD.

Related PRs

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• I have added a descriptive title to this PR.
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• I have made corresponding changes to the documentation (docs).
• I have added/update tests for my changes.

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