Prevent Symbol GC
Add documentation to MessageVerifier

[ci skip]

Complements #17727 and closes ee73d9ff8.

@lleger How do you feel about this?
remove misleading class [ci skip]
Merge pull request #17909 from sergey-alekseev/doc-change

remove misleading class [ci skip]
Merge pull request #17906 from kamipo/prevent_symbol_gc

Prevent Symbol GC
Merge pull request #17905 from claudiob/add-doc-to-message-verifier

Add documentation to MessageVerifier
Merge pull request #17910 from sergey-alekseev/remove-useless-await-close

remove unused #await_close