This PR provides gRPC client level control over Envoy generated headers. It currently controls x-envoy-internal and x-forwarded-for (can be expanded if needed)

• If true, header will be added. But it can be overridden by setting setSendInternal or setSendXff to false in
  Http::AsyncClient::StreamOptions, as per stream control.
• If false, header will be removed and can not be overridden by per stream option.

This logic is designed in this way because:

• Preserve backwards compatible behavior:
  • Both headers are still sent by default
  • If any existing users remove them with StreamOptions, headers are still removed
• Still provide the per stream override control
  • Override here implicitly means setting to false as their default value in AsyncClient::StreamOptions is true.
  • Thus, per stream override is still available, just in one-way direction: disable on per stream basis
• The only thing is that now user can not set StreamOptions to true if they are disabled in config. But it should be fine because:
  • For existing user, no one should set them to true in StreamOptions as they are already default to true.
  • For future user, per stream control can still be achieved as stated above.

Request variables

Key	Value
ref	53bf255
sha	f40b5a3
pr	34179
base-sha	f0201e5
actor	@tyxia
message	gRPC: Add support to control envoy generated headers...
started	1719461997.814156
target-branch	main
trusted	false

Container image/s (as used in this CI run)

Envoy version (as used in this CI run)