perf: add new BPS tree variations benchmarks

These add three new configs to be tested in the benchmarks: tree with
child cardinalities enabled, with inner cardinality enabled and with
both of these.

By the way simplified the performance analisys by reducing the memory
allocation overhead (it's not required to be zero-initialized) and by
moving the test tree build into a separated function.

NO_DOC=perf test
NO_TEST=perf test
NO_CHANGELOG=perf test