fix: patch wellknown types

[wenchy]

Generated descriptor from timestamp.pb.go is different with the descriptor dynamically generated by protoreflect based on source proto files.

Mixed-use of the two kinds of descriptors cause proto.Clone to panic:

panic: proto: google.protobuf.Timestamp.seconds: field descriptor does not belong to this message

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 88.38710% with 18 lines in your changes missing coverage. Please review.

Project coverage is 64.08%. Comparing base (4aca14f) to head (c7345f8). Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
internal/confgen/parser.go	71.42%	5 Missing and 3 partials :warning:
cmd/tableauc/main.go	0.00%	2 Missing :warning:
internal/confgen/util.go	86.66%	1 Missing and 1 partial :warning:
store/store.go	33.33%	1 Missing and 1 partial :warning:
xerrors/desc.go	50.00%	1 Missing and 1 partial :warning:
internal/confgen/confgen.go	50.00%	0 Missing and 1 partial :warning:
internal/fs/util.go	88.88%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #133 +/- ## ========================================== + Coverage 55.13% 64.08% +8.94% ========================================== Files 74 69 -5 Lines 9185 7342 -1843 ========================================== - Hits 5064 4705 -359 + Misses 3566 2089 -1477 + Partials 555 548 -7 ```

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