RFR: 8366522: CodeSource.getCodeSigners() throws NPE within empty certs [v4]

[Kirill Shirokov]

> The new tests cover only NPE scenarios.

Kirill Shirokov has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Make CodeSource.getCodeSigners() return empty array of CodeSigners when constructed with emtpy array of certificates. Update the jtreg test to test null/empty array combinations of certificates and code signers
 - Merge branch 'master' into JDK-8366522-fix-npe-codeSourceGetCodeSigners
 - Merge branch 'master' into JDK-8366522-fix-npe-codeSourceGetCodeSigners
 - Merge branch 'master' into JDK-8366522-fix-npe-codeSourceGetCodeSigners
 - 8366522: CodeSource.getCodeSigners() throws NPE within empty certs

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27105/files
  - new: https://git.openjdk.org/jdk/pull/27105/files/d049213f..6bfc6ecf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27105&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27105&range=02-03

  Stats: 339 lines in 99 files changed: 118 ins; 93 del; 128 mod
  Patch: https://git.openjdk.org/jdk/pull/27105.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27105/head:pull/27105

PR: https://git.openjdk.org/jdk/pull/27105