[jdk21u] RFR: 8318759: Add four DigiCert root certificates

[Rajan Halade]

Clean backport to JDK 21u

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Commit messages:
 - Backport 0ea58048f9b4cdaaa0470b2bcc03913fb3939453

Changes: https://git.openjdk.org/jdk21u/pull/363/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=363&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318759
  Stats: 459 lines in 7 files changed: 456 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u/pull/363.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/363/head:pull/363

PR: https://git.openjdk.org/jdk21u/pull/363