Surface information about the generated default timeout/retry parameters in the per-method comments

[viacheslav-rostovtsev]

This is brought on by googleapis/google-cloud-ruby#14050

The end-user does not know about the default per-rpc timeout being generated, so they just percieve the client-wide timeout to 'not have any effect'.
I propose that if we generate default timeout/retry/etc information for the method, we also add comments to the method description saying essentially,
"this method has such-and-such settings configured by default, the client-wide configuration won't override these settings".
@quartzmo suggested having a small table with the configured settings, and I think it's a great idea if we can pull it off to be consistent in all forms of documentation.