RFR: CODETOOLS-7903056: perfasm can report wrong stub name

[Nick Gasson]

This patch changes `IntervalMap::get` to check that the value falls within an interval's high/low bounds. Otherwise it returns the closest entry < value which can be misleading.

Example of the new output, where previously the `<unknown>` line reported the wrong stub routine:


 18.19%           libjvm.so  ProgrammableUpcallHandler::on_entry
 13.94%                      <unknown>
  9.39%           libjvm.so  ProgrammableUpcallHandler::on_exit
  8.36%         c2, level 4  java.lang.invoke.LambdaForm$MH.0x00000008001b8400::invoke, version 1595

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Commit messages:
 - CODETOOLS-7903056: perfasm can report wrong stub name

Changes: https://git.openjdk.java.net/jmh/pull/54/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmh&pr=54&range=00
  Issue: https://bugs.openjdk.java.net/browse/CODETOOLS-7903056
  Stats: 26 lines in 1 file changed: 20 ins; 0 del; 6 mod
  Patch: https://git.openjdk.java.net/jmh/pull/54.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/54/head:pull/54

PR: https://git.openjdk.java.net/jmh/pull/54