[jdk25u] RFR: 8365086: CookieStore.getURIs() and get(URI) should return an immutable List

[Kieran Farrell]

Clean backport

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Commit messages:
 - bp

Changes: https://git.openjdk.org/jdk25u/pull/319/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u&pr=319&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8365086
  Stats: 127 lines in 2 files changed: 119 ins; 4 del; 4 mod
  Patch: https://git.openjdk.org/jdk25u/pull/319.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u.git pull/319/head:pull/319

PR: https://git.openjdk.org/jdk25u/pull/319