[foreign] RFR 8211925: Remove jdk.internal.clang from list of upgradeable modules

[Maurizio Cimadamore]

Hi,
while ago, to get the Jextract-FFI test working we added (as a short 
term measure) jdk.internal.clang and jdk.jextract to th elist of 
upgradeable modules. Itis now time to revert that, since this is causing 
issues with tier1 tests in jdk_lang group. This pathc reverts that 
change and, instead, uses --patch-module to achieve same effect.

Webrev:

http://cr.openjdk.java.net/~mcimadamore/panama/8211925/

Cheers
Maurizio