For the spec to pass linting.

For the spec to pass linting.

The examples under <repo_root>/examples now rely on the released
versions. Those under src/objective-c/examples, as well as the tests,
rely on protoc and the plugin as compiled from head.

Still needed:

- Make it build protoc if it’s not in the root (i.e. if we're developing locally)
- Put the gRPC plugin in the GitHub release page, and add a podspec for it that does the same

The protobuf commit conflicted. Resolved to the latest one.

Add http2 status code in error_message if it's not 200

Contributed cmake project files.

It’s just the merge of beta-3.1 and beta-3.2, both of which we need.

Removed invalid sentence from interop flag description

Fix memory leak, fix error.c refcount reporting

Build objective-c examples as part of automatic tests

Conflicts:
- gRPC.podspec
  - Only had non-trivial changes in the core file list, which will need to be
    regenerated (in gRPC-Core.podspec).
- src/objective-c/BoringSSL.podspec
  - Had trivial conflicts in the version.
- src/objective-c/examples/RemoteTestClient/RemoteTest.podspec
  - Trivial conflicts in quoting.
- src/objective-c/examples/Sample/Sample.xcodeproj/project.pbxproj and
src/objective-c/examples/SwiftSample/SwiftSample.xcodeproj/project.pbxproj
  - The master version is used, pending testing. The 0.14 version had emoji and
    some unneeded entries.
- src/objective-c/tests/Podfile
  - Added CronetFramework pod, and warning silencing from master.
- templates/gRPC.podspec.template
  - Deleted.
- third_party/protobuf
  - Using master commit, but need to verify if it works for frameworks.

Add a maybe-temporary way for apps to clear the channel cache

fix for working with compressed data. Fixes #6746.

Use open-source defaults to propagate Python plugin configuration

Fix bug with override_server flag in run_interop_tests.py

Dont create errors redundently in chttp2_transport.c

implemented eventfd_check_availability

Fix Python server interop spec noncompliance

PHP: fix shutdown hang issue

Updated git clone URL

fixed size_t format string

Changed default string type to be str

Build experimental nugets with dotnet CLI

Fix Cocoapods linter issues with gRPC-Core.podspec

Make transport-level errors be reflected in status messages on calls