RFR(S) [15] : 8249000 : vm.gc.X should take selected JIT into account

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev/8249000/webrev.00/
> 241 lines changed: 34 ins; 5 del; 202 mod;


Hi all,

could you please review the patch which modifies requires/VMProps to set vm.gc.X to false if Graal is selected and X GC isn't supported by Graal?

the patch also replaces @requires similar to `vm.gc.X & !vm.graal.enabled` w/ `vm.gc.X` where it's applicable.

from JBS:
> not all GCs are supported by Graal JIT, which leads to failures like JDK-8247527 and boilerplate fixes like replacing all `@requires vm.gc.Z` w/ `@requires vm.gc.Z & !vm.graal.enabled`. 
> 
> as vm.gc.X means that X GC can be selected, it would be more natural, less surprising, and much more clear to have it true if the selected JIT supports the said X GC.

webrev: http://cr.openjdk.java.net/~iignatyev/8249000/webrev.00/
JBS: https://bugs.openjdk.java.net/browse/JDK-8249000
testing: test/hotspot/jtreg/{gc,compiler,runtime,serviceability} on {linux,windows,macos}-x64 w/ and w/o Graal as JIT

Thanks,
-- Igor