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)

feat: updated CHANGELOG for 2020-07 release (googleapis#4452)

feat: updated CHANGELOG for 2020-06 release (googleapis#4318)

doc: update release notes for v1.13.0 (googleapis#3985)

chore: update CHANGELOGS for release (googleapis#3636)

* chore: update CHANGELOGS for release

chore: update release notes (googleapis#3414)

chore: update release notes (googleapis#3385)

chore: release notes for v0.18.x (googleapis#3368)

Also update the ABI dumps.

chore: update readmes for release (googleapis#3306)

* chore: update readmes for release

* PR comments

chore: update release notes for v0.16 (googleapis#3284)

Includes the fix for corrupted resumable uploads.