Eliminate redundant attribute reads in validation

The validator was reading all string attributes in addition to the
attribute reads in PackageParsing. Eliminating the attribute reads
from the validator and instead validating at the time when attributes
are read in PackageParser further reduces the performance regression
to ~5%. The mean times measured on a lynx devices are:

PackageParsingPerfTest#sequentialNoCache[v1]_new_ns: 748223578
PackageParsingPerfTest#sequentialNoCache[v1]_old_ns: 790309363
PackageParsingPerfTest#sequentialNoCache[v1]_none_ns: 717520130

Bug: 289190523, 267185315
Test: atest PackageParsingPerfTest
Test: atest AndroidPackageParsingValidationTest
Change-Id: I53e3606a48fd97b2e27e41f34bb83029ab908807