[11u] RFR: 8223260: NamingManager should cache InitialContextFactory

[Severin Gehwolf]

Hi,

Could I please get a review for this JDK 11 backport? I'd like to
backport this for Oracle JDK 11.0.7 parity. The JDK 15 patch applies
cleany, but it doesn't build and the test needed a slight modification:

 * JDK 11u doesn't have java.io.Serial (14+ only). I've removed it from
   the patch in class FactoryInitializationError.
 * JDK 15 has JarUtils consolidated, and thus, the test needed an
   additional /lib/testlibrary @libray while at the same time dropping
   the jdk.test.lib.util.JarUtils import.

Otherwise the patch is the same as in JDK 15.

Bug: https://bugs.openjdk.java.net/browse/JDK-8223260
webrev: http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8223260/01/webrev/
original change: https://hg.openjdk.java.net/jdk/jdk/rev/92b01977fde2

Testing: tier 1 tests and javax/naming tests. Including the new
regression test, which fails before and passes after patch.

Thoughts?

Thanks,
Severin