RFR: 8341775: Duplicate manifest files are removed by jarsigner after signing [v3]

[Kevin Driver]

> JDK-8341775: In the case where there is a *single* META-INF directory but potentially *multiple* manifest files of different cases, print a warning before selecting the first one and ignoring the rest (the current behavior should be maintained).
> 
> **Note**: We cannot (so far) pass whether the verbose flag is set to the class that does this processing. We may want to add a property to the builder for this. As-is, the message will be printed via `System.err` whether verbose is set or not.

Kevin Driver 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 three additional commits since the last revision:

 - Merge branch 'master' of https://github.com/openjdk/jdk into 8341775
   # Please enter a commit message to explain why this merge is necessary,
   # especially if it merges an updated upstream into a topic branch.
   #
   # Lines starting with '#' will be ignored, and an empty message aborts
   # the commit.
 - Merge branch 'master' of github.com:openjdk/jdk into 8341775
   # Please enter a commit message to explain why this merge is necessary,
   # especially if it merges an updated upstream into a topic branch.
   #
   # Lines starting with '#' will be ignored, and an empty message aborts
   # the commit.
 - JDK-8341775: In the case where there is a *single* META-INF directory but potentially *multiple* manifest files of different cases, print a warning before selecting the first one and ignoring the rest.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22222/files
  - new: https://git.openjdk.org/jdk/pull/22222/files/b2fe8124..6e61c2ed

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22222&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22222&range=01-02

  Stats: 7159 lines in 140 files changed: 5804 ins; 773 del; 582 mod
  Patch: https://git.openjdk.org/jdk/pull/22222.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22222/head:pull/22222

PR: https://git.openjdk.org/jdk/pull/22222