[balsa] Fix 304WithBody test and add new one.

[bencebeky]

Add //test/common/http/http1:codec_impl_test test case for 304 response
with body for both BalsaParser and http-parser. In this test, the body
is dispatched to the parser in the same Parser::execute() call as the
headers.

Modify ProtocolIntegrationTest.304WithBody by appending '\r\n' to the
end of the "body" of the 304 response, necessary for BalsaParser to
signal an error.

Tracking issue: #21245

Also include #24003 (GitHub does not support dependent PRs)

Signed-off-by: Bence Béky bnc@google.com

Commit Message: [balsa] Fix 304WithBody test and add new one.
Additional Description:
Risk Level: low, test-only change
Testing: //test/integration:protocol_integration_test
Docs Changes: n/a
Release Notes: n/a
Platform Specific Features: n/a

[repokitteh-read-only]

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🐱

Caused by: #24058 was opened by bencebeky.

see: more, trace.

[bencebeky]

Now that #24003 landed, abandoning in favor of a new PR with clean history. The only purpose of this temporary PR was to see if presubmits pass, and if not, be able to start working on that while waiting for #24003.