Merge pull request grpc#12320 from dgquintas/release_1.6.0

Release 1.6.0 version number change

Merge pull request grpc#12292 from stanley-cheung/php-backport-1_6-fe…

…atures

PHP: backport master features into v1.6.x branch

Merge pull request grpc#12241 from stanley-cheung/bump-to-1_4_7

Bump to version 1.4.7

Merge pull request grpc#12202 from stanley-cheung/bump-to-1_4_6

Bump to 1.4.6

Merge pull request grpc#12133 from apolcyn/bump_to_145

Bump version to 1.4.5

Merge pull request grpc#12121 from stanley-cheung/bump-to-1_4_4

Bump to version 1.4.4

Merge pull request grpc#12085 from stanley-cheung/bump-to-1_4_3

Bump version to 1.4.3

Merge pull request grpc#11713 from muxi/advance-version-v1.4.2

Advance version to v1.4.2

Merge pull request grpc#11620 from murgatroid99/version_bump_1.4.1

Bump version to 1.4.1

Merge pull request grpc#11567 from muxi/fix-objc-memory-leak-v14

Backport grpc#11521: Fix objc memory leak v14