Refactor reading `OatFile::BssMappingInfo`.

Use common code for reading .bss mappings for `OatDexFile`
and `bcp_bss_info_[.]`. This can help avoid bugs where we
update one and forget to update the other. Also update
error messages to differentiate between the two cases.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 335793499
Change-Id: I478b6bea7205ba3d53f6efafc906595e866d2c72