Please add caching for regex pattern in `PerfMetricValidator#validateAttribute`

[PiotrBandurski]

During debugging performance issues I found out that sdk is not caching regexes which can add additional computation overhead (which is performed on main thread since sdk adds listener to fragment manager)

Problem is here PerfMetricValidator#validateAttribute(:

firebase-android-sdk/firebase-perf/src/main/java/com/google/firebase/perf/metrics/validator/PerfMetricValidator.java

Line 167 in a362e45

if (!key.matches("^(?!(firebase_|google_|ga_))[A-Za-z][A-Za-z_0-9]*")) {

Here is example from method sampling (I know this does not show real timming but in my case it takes 1/3 of computation time in trace)

[google-oss-bot]

I couldn't figure out how to label this issue, so I've labeled it for a human to triage. Hang tight.

[rlazo]

Hi @PiotrBandurski thanks a lot for your report! #6865 should address this issue.

[rlazo]

The fix has been submitted and it will be part of the next release. Thanks again for the report @PiotrBandurski !