gRPC API: Add support to control the internal request headers

[tyxia]

This is the follow-up of https://github.com/envoyproxy/envoy/pull/34125.

https://github.com/envoyproxy/envoy/pull/34125 provides the way to remove x-envoy-internal and x-forwarded-for in http asyncClient path. This API PR provides the config options for envoy-gRPC (which is on top of http asyncClient) to remove x-envoy-internal and x-forwarded-for.

By default, those two config options are TRUE, which keeps the existing behavior. And next in the impl, envoy-gRPC client can config these two options(setting them to FALSE) to not add those two headers.

[repokitteh-read-only[bot]]

As a reminder, PRs marked as draft will not be automatically assigned reviewers, or be handled by maintainer-oncall triage.

Please mark your PR as ready when you want it to be reviewed!

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/34179 was opened by tyxia.

see: more, trace.

[repokitteh-read-only[bot]]

CC @envoyproxy/api-shepherds: Your approval is needed for changes made to (api/envoy/|docs/root/api-docs/). envoyproxy/api-shepherds assignee is @lizan CC @envoyproxy/api-watchers: FYI only for changes made to (api/envoy/|docs/root/api-docs/).

:cat:

Caused by: https://github.com/envoyproxy/envoy/pull/34179 was opened by tyxia.

see: more, trace.

[tyxia]

/assign @htuch @lizan

PTAL, Thanks!

[jmarantz]

/wait (for CI to be made green)

[tyxia]

/retest

[tyxia]

/retest