[crac] RFR: Make CheckpointException/RestoreException aggregate-only [v8]

[Radim Vansa]

> CheckpointException and RestoreException (both jdk.crac and javax.crac) cannot carry any message, cause and don't collect stack trace. The sole purpose of these is to aggregate other exceptions in suppressed exceptions.

Radim Vansa has updated the pull request incrementally with one additional commit since the last revision:

  Update javadoc, make final

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Changes:
  - all: https://git.openjdk.org/crac/pull/64/files
  - new: https://git.openjdk.org/crac/pull/64/files/50926f02..78dcaca2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=crac&pr=64&range=07
 - incr: https://webrevs.openjdk.org/?repo=crac&pr=64&range=06-07

  Stats: 24 lines in 4 files changed: 8 ins; 8 del; 8 mod
  Patch: https://git.openjdk.org/crac/pull/64.diff
  Fetch: git fetch https://git.openjdk.org/crac.git pull/64/head:pull/64

PR: https://git.openjdk.org/crac/pull/64