Found new plugin versions (#2165)

Add grpc/swift-protobuf v2.1.2 (#2161)

Needed an update to the dependencies (related to #1941). For context,
the steps were (from the plugin's directory):

```
$ git clone --depth 1 --branch 2.1.2 https://github.com/grpc/grpc-swift-protobuf --recursive
$ cd grpc-swift-protobuf
$ swift package resolve
$ mv Package.resolved ../
```

Probably a good reason to look to automate this now.

Fixes #2160.

Update protobuf-es (#2154)

Update ts-proto to last stable 1.x version (#2148)

Added the latest stable 1.x version of ts-proto

Update bufbuild/validate-java (#2143)

Update protoc, connectrpc/python, and pgv plugins (#2139)

Add tonic-prost crate dependency to tonic 0.5.0 (#2129)

This was changed upstream, perhaps unintentionally, but our crates now
need to pull in tonic-prost explicitly or they will fail to compile.

Ref:
hyperium/tonic@969408e#r171907626

Add `flat_output_dir` option to prost-tonic 0.5.0 (#2125)

Similar to #2123.

Enable `flat_output_dir` option for prost 0.5.0 (#2123)

The BSR's cargo registry expects a certain file structure from the
plugin for generating the lib.rs file that creates the package. This
changed from 0.4.0 to 0.5.0; enable this option so that 0.5.0 matches
the 0.4.0 output.

Ref: neoeinstein/protoc-gen-prost#89

Update prost and grpc-go plugins (#2120)