RFR: 8338626: ClassLoaderExt::process_jar_manifest() should allow / separator on Windows [v2]

[Calvin Cheung]

> On Windows, we can use '/' as the file separator in the classpath but not in the `Class-Path:` attribute.
> This patch is to enable the use of '/' as the file separator in the `Class-Path:`attribute on Windows.
> 
> Passed tiers 1 - 3 testing.

Calvin Cheung has updated the pull request incrementally with one additional commit since the last revision:

  @iklam comment

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Changes:
  - all: https://git.openjdk.org/jdk/pull/20924/files
  - new: https://git.openjdk.org/jdk/pull/20924/files/335a0aae..f0ecad80

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20924&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20924&range=00-01

  Stats: 42 lines in 2 files changed: 37 ins; 1 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/20924.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20924/head:pull/20924

PR: https://git.openjdk.org/jdk/pull/20924