RFR: 8296142: CertAttrSet::(getName|getElements|delete) are mostly useless

[Weijun Wang]

This code change removes `getElements()` and `delete()` from `CertAttrSet` and all its subclasses. The `getName()` method is moved to `s.s.x.Extension` since it's only useful there.

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Commit messages:
 - the fix

Changes: https://git.openjdk.org/jdk/pull/10934/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10934&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8296142
  Stats: 1191 lines in 41 files changed: 33 ins; 1135 del; 23 mod
  Patch: https://git.openjdk.org/jdk/pull/10934.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10934/head:pull/10934

PR: https://git.openjdk.org/jdk/pull/10934