RFR: 8320362: Load anchor certificates from Keychain keystore [v2]

[Alexey Bakhtin]

> Please review the proposed fix.
> 
> The patch loads system root certificates from the MacOS Keychain with TrustSettings.
> It allows to build a trusted certificate path using the MacOS Keychain store only.

Alexey Bakhtin has updated the pull request incrementally with one additional commit since the last revision:

  Mark trust anchor certificates readonly

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16722/files
  - new: https://git.openjdk.org/jdk/pull/16722/files/b0d91794..db98b7c2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16722&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16722&range=00-01

  Stats: 33 lines in 2 files changed: 21 ins; 5 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/16722.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16722/head:pull/16722

PR: https://git.openjdk.org/jdk/pull/16722