Add HTTP2_CODE_COUNT_N API and decompress_failure_3 counters to debug source of DECOMPRESS_FAILURE errors. Note that on any code path multiple of these macros are expected to be hit. gfe-relnote: n/a, add CODE_COUNT macros for debugging. PiperOrigin-RevId: 292355227 Change-Id: I9b02119c30af03016073307feedee896f397b24c