Replace binderdebug regex

It's incredibly slow!
Walking through the text using android-base/strings.h and std::string
operations is much faster.
We are making the same assumptions about the format of the files as we
were with regex, but we have fewer hard requirements for the format now.

See bug for detailed timing results with simpleperf.

Test: atest binderdebug_tests
Bug: 270596767
Change-Id: I674414504050371083aad7a93714114190e8a2b4