Roll Dart Protobuf Support from 1d175bef6043 to ba29983968de (5 revisions)

https://dart.googlesource.com/protobuf/+log/1d175bef6043..ba29983968de

2022-10-18 omersa@google.com protoc_plugin: Reword some of the documentation (#766)
2022-10-18 omersa@google.com protoc_plugin: Improve "is map field" check (#765)
2022-10-18 omeragacan@gmail.com Update CHANGELOG: mention #751
2022-10-18 omeragacan@gmail.com Add CHANGELOG entry for #760, #763
2022-10-18 omersa@google.com Fix `null` handling in proto3 JSON deserializer (#763)

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/dart-protobuf-dart-sdk
Please CC dart-ecosystem-gardener@grotations.appspotmail.com on the revert to ensure that a human
is aware of the problem.

To file a bug in Dart Protobuf Support: https://github.com/dart-lang/protobuf/issues
To file a bug in Dart SDK: https://github.com/dart-lang/sdk/issues

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https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
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Tbr: dart-ecosystem-gardener@grotations.appspotmail.com
Change-Id: I5502c8ee170701888956534cbd92473a24435fea
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/264664
Reviewed-by: Nate Bosch <nbosch@google.com>
Commit-Queue: Nate Bosch <nbosch@google.com>

DEPS

@@ -149,7 +149,7 @@ vars = {
   "path_rev": "9955b27b9bb98d87591208e19eb01c51d29fd467",
   "ply_rev": "604b32590ffad5cbb82e4afef1d305512d06ae93",
   "pool_rev": "fa84ddd0e39f45bf3f09dcc5d6b9fbdda7820fef",
-  "protobuf_rev": "1d175bef6043bc4bdef5970f6dbd6d3001124373",
+  "protobuf_rev": "ba29983968de5b54196c6c2a5cff1afbdda24ae2",
   "pub_rev": "b9afe9270c24d040b8ae465b4b37ba4f7f4b4cc5", # manually rev'd
   "pub_semver_rev": "7671359982b4be9bdf87e621dd1bcdeac242b4b9",
   "root_certificates_rev": "692f6d6488af68e0121317a9c2c9eb393eb0ee50",