Increase xdebug_nesting_level for extended editions scenarios

Actual:
xdebug.max_nesting_level is set to 200 but default is 256 and even 256 is not enough for some scenarios.

Expected:
xdebug.max_nesting_level is set to 256 by default. Documentation reflects the possibility of issues with nesting level setting and describes the workaround.

More details: https://jira.corp.magento.com/browse/MC-5828