RFR: 8163371: Enable tracing which JLI classes can be pre-generated

[Claes Redestad]

Hi,

please review this change which adds a means to trace what
LFs and BMH classes we try to resolve at runtime (and whether
we failed or succeeded), along with an update to the
--generate-jli-classes plugin to take as it's input a file containing
the output of such tracing.

Bug: https://bugs.openjdk.java.net/browse/JDK-8163371
Webrev: http://cr.openjdk.java.net/~redestad/8163371/webrev.01/

I picked a random use case to test/verify the implementation in
a minimal nashorn script, bin/jjs exit.js[1].

1. On my local JDK image this loads 2359 classes.
2. On a jlink image with --generate-jli-classes=@empty to
disable the default pre-generation, 2450 classes are loaded
3. On a jlink image built with the output of a tracing run[2],
2114 classes are loaded

Also, inspecting the output shows that a total of 42
BoundMethodHandle$Species_* classes were pregenerated in case
number 3, compared to 37 in the default case and 0 on the image
with no pregeneration, meaning we avoid generating a total of 378
classes at runtime.

As a follow up I plan to add tests and explore the benefits of
adding a way to generate and use a relevant list of jli classes in the
build (adding to the existing CDS classlist generation mechanism
seems appropriate).

Thanks!

/Claes

[1]
exit.js:
exit();

[2]
bin/jjs -J-Djava.lang.invoke.MethodHandle.TRACE_RESOLVE=true exit.js > 
trace.out
bin/jlink ... --generate-jli-classes=@trace.out