RFR: 8255696: JDWP debug agent's canSuspendResumeThreadLists() should be removed

[Chris Plummer]

This RFR removes the debug agent's canSuspendResumeThreadLists() function and code that depends on it. Please see the CR for a description of why this is being done.

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Commit messages:
 - Remove canSuspendResumeThreadLists().

Changes: https://git.openjdk.java.net/jdk/pull/970/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=970&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255696
  Stats: 33 lines in 3 files changed: 0 ins; 29 del; 4 mod
  Patch: https://git.openjdk.java.net/jdk/pull/970.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/970/head:pull/970

PR: https://git.openjdk.java.net/jdk/pull/970