Abbreviate or drop Java package names when rendering stacks - #4

Why

Java frames in a flame graph are dominated by their package names. io.netty.channel.epoll.Native.epollWait0 is mostly io.netty.channel.epoll., which leaves little room in a frame's box for the class and method that say what it is.

What changes

jonoffcpu-correlator.jar stacks gains --package-names full|abbreviate|drop:

• Only package-qualified Class.method frames are changed. Nested and hidden classes keep their names (a.Outer$Inner.<init>, j.l.i.LambdaForm$MH/0x….invoke). Anything else — native frames such as epoll_wait or libc.so.6, [stack unavailable], and frames without a package — is left as it is.
• Only the display changes:
  • --include/--exclude still match the full names, so existing patterns keep working.
  • Stacks that become identical (for example app.one.Worker.park and app.two.Worker.park under drop) merge into one line, and their time is summed.
  • --summary records the mode as packageNames.
• full is the default, so a default rendering still reproduces jonoffcpu-offcpu-stacks.collapsed byte for byte.
• The option works with every other stacks option, including --time.
• Documented in README §5 and OFFLINE.md.

Verification

• ./gradlew spotlessCheck :jonoffcpu-correlator:check passes. A new StackProfileTest case covers:
  • the frame rule on qualified, nested, hidden-class, unqualified and native names;
  • a rendered profile in each mode, including two stacks merging under drop;
  • filters matching full names under drop;
  • the summary field;
  • an invalid mode.
• On the Pulsar broker profile (10,631 lines):
  • full reproduces the collapsed file byte for byte;
  • abbreviate shrinks the file from 14.0 MB to 10.6 MB and drop to 9.1 MB, with the same total time.