[chore][component] Document component.Host expectations

[mx-psi]

Description

Adds a note to the component.Host interface documenting that components may require additional interfaces.
I think this is the only sustainable pattern post 1.0, since we won't be able to add any new methods to the component.Host interface.

This pattern is also used today by:

• The zpages extension (

  opentelemetry-collector/extension/zpagesextension/zpagesextension.go

  Lines 58 to 66 in 91f13c3

  	hostZPages, ok := host.(interface {
  	RegisterZPages(mux *http.ServeMux, pathPrefix string)
  	})
  	if ok {
  	hostZPages.RegisterZPages(zPagesMux, "/debug")
  	zpe.telemetry.Logger.Info("Registered Host's zPages")
  	} else {
  	zpe.telemetry.Logger.Warn("Host's zPages not available")
  	}

  )
• The receiver creator (after [receiver/receivercreator] Make receivercreator expose its required interface opentelemetry-collector-contrib#34234)
• Some contrib components ([chore] Remove all direct usage of component.host.GetExporters opentelemetry-collector-contrib#32498)

Link to tracking issue

Fixes #10181

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.24%. Comparing base (3caaf16) to head (6deb763).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #10720   +/-   ##
=======================================
  Coverage   92.24%   92.24%           
=======================================
  Files         403      403           
  Lines       18720    18720           
=======================================
  Hits        17268    17268           
  Misses       1097     1097           
  Partials      355      355           

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