RFR: 8199471: Enable generation of callSiteForms at link time

[Claes Redestad]

Hi,

LFs generated via Invokers.callSiteForm only depend on the 
MethodTypeForm and link type,
and can be generated ahead of time by jlink --generate-jli-classes:
Webrev: http://cr.openjdk.java.net/~redestad/8199471/open.00/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8199471

The current training runs done during build shows this is somewhat 
effective at reducing
the number of LF classes we generate at runtime, avoiding spinning up up 
to 6 classes
during bootstrap.

Thanks!

/Claes