[jdk11u-dev] RFR: 8317374: Add Let's Encrypt ISRG Root X2

[Severin Gehwolf]

Unclean backport, but got resolved trivially. Pattern matching for switch isn't present in 11u. Test change in `VerifyCACerts.java` has slightly different context. Fixed those issues manually. Please review!

Testing:
- [ ] GHA (still running)
- [x]  `test/jdk/sun/security/lib/cacerts` and `test/jdk/security/infra/java/security/cert/CertPathValidator` tests. All pass (including the new one `CAInterop.java#letsencryptisrgx2`

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Commit messages:
 - Fix whitespace
 - Backport e6f46a43268808d0cbbb3bb93c73aa8e4cbfad83

Changes: https://git.openjdk.org/jdk11u-dev/pull/2280/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2280&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317374
  Stats: 39 lines in 3 files changed: 35 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2280.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2280/head:pull/2280

PR: https://git.openjdk.org/jdk11u-dev/pull/2280