RFR: 8344248: Remove Security Manager dependencies from java.security.jgss and jdk.security.jgss modules

[Sean Mullan]

Now that JEP 486 has been integrated, `java.security.jgss` and `jdk.security.jgss` module dependencies on `System.getSecurityManager` and `AccessController.doPrivileged*` can be removed.

There is an undocumented property named "sun.security.krb5.autodeducerealm" that can probably be removed as it only affected behavior when an SM was enabled; however I have left the code that reads the property as-is (see sun/security/krb5/Realm.java) and have opened a separate issue to determine if it can be safely removed.

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Commit messages:
 - Initial cleanup.

Changes: https://git.openjdk.org/jdk/pull/22256/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22256&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344248
  Stats: 876 lines in 42 files changed: 23 ins; 589 del; 264 mod
  Patch: https://git.openjdk.org/jdk/pull/22256.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22256/head:pull/22256

PR: https://git.openjdk.org/jdk/pull/22256