oe-build-perf-test: pack all buildstat in one file
Write out all buildstats into one big json file, instead of using
multiple per-measurement files. Individual buildstats will be indexed
using "<test_name>.<measurement_name>" as the key. Also, changes the
per-testcase working directories into temporary directories that will be
removed after test execution as there are no more per-testcase data files
to store permanently.
[YOCTO #10582]
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
