Replace various //go:generate lines and regenerate.sh scripts with a
single, top-level regenerate.sh that regenerates all .pb.go files.
Placing generation in a single script ensures that all files are
generated with similar parameters. The new regenerate.sh uses the
protoc-gen-go version defined in test/tools/go.mod and automatically
handles new .proto files as they are added.
Do some minor refactoring on .proto files: Every file now has a
go_package option (which will be required by a future version of the
code generator), and file imports are all relative to the repository
root.
* Modified tests to use tlogger.
* Fail on errors, with error expectations.
* Added expects and MixedCapsed grpclb_config tests
* Moved tlogger to grpctest, moved leakcheck tester to grpctest.go
* Added ExpectErrorN()
* Removed redundant leak checks
* Fixed new test
* Made tlogger globals into tlogger methods
* ErrorsLeft -> EndTest
* Removed some redundant lines
* Fixed error in test and empty map in EndTest
* service reflection can lookup enum, enum val, oneof, and field symbols; cache descriptors
* address feedback: don't use mutex, remove unnecessary conditional, make fileDescContainingExtension a func instead of a method
