RFR: 1625: Validate input from /summary command [v2]

[Zhao Song]

> 1.  Added validation to SummaryCommand.
> 2. If exceptions are thrown when the bot is evaluating the current status of the pr, the exceptions will be treated as integration blocker.

Zhao Song has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  SKARA-1625

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Changes:
  - all: https://git.openjdk.org/skara/pull/1401/files
  - new: https://git.openjdk.org/skara/pull/1401/files/ba55baae..15cc6c8c

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1401&range=01
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1401&range=00-01

  Stats: 31 lines in 4 files changed: 18 ins; 3 del; 10 mod
  Patch: https://git.openjdk.org/skara/pull/1401.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1401/head:pull/1401

PR: https://git.openjdk.org/skara/pull/1401