RFR: 8300140: ZipFile.isSignatureRelated returns true for files in META-INF subdirectories [v12]

[Eirik Bjorsnos]

> Some call sites of SignatureFileVerifier.isBlockOrSF fails to check that files reside in META-INF directly, and not in a subdirectory of META-INF.
> 
> The mentioned call sites needs updates to check and ignore such files.
> 
> A new test VerifyUnrelatedSignatureFiles is added which verifies that [*.SF, *.RSA] files in META-INF/ subdirectories are indeed ignored.

Eirik Bjorsnos has updated the pull request incrementally with two additional commits since the last revision:

 - Link to a more recent version of the JAR File Specification
 - Add test coverage for matching of custom SIG-* files in SignatureFileVerifier.isSigningRelated

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11976/files
  - new: https://git.openjdk.org/jdk/pull/11976/files/34873625..de3c6781

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11976&range=11
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11976&range=10-11

  Stats: 64 lines in 2 files changed: 56 ins; 5 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/11976.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11976/head:pull/11976

PR: https://git.openjdk.org/jdk/pull/11976