[coverage] Remove subtrees and benchmarks from coverage report
Summary:
Removes stats about leveldb, univalue, and benchmark coverage from the coverage reports. Since we don't test these three items specifically and thus don't care about test coverage for these items. This builds on top of #10511 to use the faster lcov -r replacement.
Backport of core PR10565 and PR11443
https://github.com/bitcoin/bitcoin/pull/10565/files
https://github.com/bitcoin/bitcoin/pull/11443/files
Depends on D3565
Test Plan:
../configure --enable-lcov make make cov
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D3545