sstatesig: Improve the support for locked down sstate cache usage

sstatesig: Improve the support for locked down sstate cache usage

Add code in the sstate hash validation code to ensure it really did
install these from sstate since if it didn't should to warn/abort
the build. The judgment condition is:
1) If a build is replaced by locked sstate-cache, it will triger a
   warn/error;
2) If objects are not used from the locked cache, it will triger a
   warn/error;
3) Use SIGGEN_LOCKEDSIGS_CHECK_LEVEL variable controls whether this
   is just a warning or a fatal error or nothing to report.

[YOCTO #6639]

(From OE-Core rev: 305912dce61c4fed0cbf631aa98a9e6f29db88e4)

(From OE-Core rev: 1683815695f39d4bad352348913f927ac8a1bcf5)

Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>