[configauth] The configauth.Authentication should be suffixed with Config or rename to Config.

[bogdandrutu]

See the rules: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/coding-guidelines.md#configuration-structs
See the code: https://github.com/open-telemetry/opentelemetry-collector/blob/main/config/configauth/configauth.go#L26

[bogdandrutu]

cc @mx-psi for the blocking issue for the configauth stabilization.

[mx-psi]

#12904 fixes this