Contrib coverage (envoyproxy#19867)

fix the issue that bazel coverage doesn't do coverage of source code in contrib

Fixes envoyproxy#19729

Signed-off-by: Felix Du <durd07@gmail.com>

.bazelrc

@@ -167,7 +167,7 @@ build:coverage --strategy=CoverageReport=sandboxed,local
 build:coverage --experimental_use_llvm_covmap
 build:coverage --collect_code_coverage
 build:coverage --test_tag_filters=-nocoverage
-build:coverage --instrumentation_filter="//source(?!/common/quic/platform)[/:],//include[/:]"
+build:coverage --instrumentation_filter="//source(?!/common/quic/platform)[/:],//include[/:],//contrib(?!/.*/test)[/:]"
 build:test-coverage --test_arg="-l trace"
 build:fuzz-coverage --config=plain-fuzzer
 build:fuzz-coverage --run_under=@envoy//bazel/coverage:fuzz_coverage_wrapper.sh