scripts/resulttool/regression: add metadata filtering for oeselftest

scripts/resulttool/regression: add metadata filtering for oeselftest

When generating regression reports, many false positive can be observed since
some tests results are compared while the corresponding tests sets are not the
same, as it can be seen for example for oeselftest tests (oeselftest is run
multiple time but with different parameters, resulting in different tests sets)

Add a filtering mechanism in resulttool regression module to enable a better
matching between tests. The METADATA_MATCH_TABLE defines that when the TEST_TYPE
is "oeselftest", then resulttool should filter pairs based on
OESELFTEST_METADATA appended to test configuration. If metadata is absent from
test results, in order to keep compatibility with older results, add a
"guessing" mechanism to generate the missing OESELFTEST_METADATA. The guessed
data is tightly coupled to the autobuilder configuration, where all oe-selftest
executions are described

Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>