chore: update CHANGELOG and ABI dumps (googleapis#5786)

* chore: update CHANGELOG and ABI dumps

chore: prepare for v1.23.0 release (googleapis#5708)

* chore: prepare for v1.23.0 release

Update release notes and API baselines.

chore: prepare for v1.22.0 release (googleapis#5690)

Update release notes and API baselines.

chore: december release notes and ABI update (googleapis#5566)

chore: november release notes and ABI update (googleapis#5396)

refactor(generator): use common version and inline namespace for gene…

…rated code (googleapis#5174)

* refactor(generator): use common version and inline namespace for generated code

doc: update CHANGELOG for v1.18.0 (googleapis#5060)

* doc: update CHANGELOG for v1.18.0

doc: update changelog and bump versions for dot release (googleapis#5013

)

doc: update CHANGELOG for v1.17.0 release (googleapis#5001)

* doc: update CHANGELOG for v1.17.0 release

doc: update CHANGELOG for 2020-08 release (googleapis#4768)

* doc: update CHANGELOG for 2020-08 release

* address review comments

* some formatting tweaks

* nix a couple stray periods

* address review comments

* add new change (4746)