pw_grpc: Skip HTTP2 frame payload for frames that result in stream reset

When receiving invalid frames from a client, some errors result in
stream reset (force closure), and some errors result in connection
closure.

If the error only results in stream reset, the rest of the frames sent
in the connection should be readable by the server. This means that the
entire frame should be skipped over, with normal connection processing
happening after.

Previously, the code did not skip past the payload for DATA and HEADERS
frames that resulted in a stream-reset error. Thus, when continuing to
process the connection, the payload of the frame would be interpreted as
the header of the next frame, resulting in a cascade of failures.

This commit fixes the issue by ensuring that, for frames with a payload,
the payload is skipped when encountering a stream-reset error. For
errors that result in a connection error (GOAWAY), there are no changes.

Test: Set up a situation where the client sends a DATA frame with a
Test: payload on a stream that the server has already closed.
Test: Observe that the server recognizes this is data for a closed
Test: stream, and that subsequent frames are received and interpreted
Test: correctly.
Change-Id: Id1e11b74d9fccdeb7285e2455f2675328ac7da91
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/230951
Reviewed-by: Erik Gilling <konkers@google.com>
Commit-Queue: Eli Lipsitz <elipsitz@google.com>
Lint: Lint 🤖 <android-build-ayeaye@system.gserviceaccount.com>
Reviewed-by: Austin Foxley <afoxley@google.com>
Presubmit-Verified: CQ Bot Account <pigweed-scoped@luci-project-accounts.iam.gserviceaccount.com>