Cover java.lang.Package with tests.

Cover Package#getSpecificationVendor, Package#getSpecificationVersion,
Package#isCompatibleWith, and Package#isSealed methods with unit
tests.

Bug: 182166988
Test: atest libcore.java.lang.PackageTest
Change-Id: I50cfd43a318d4256a324de1c04b10544cd791e7c
1 file changed