RFR: 8284047: Harmonize/Standardize the SSLSocket/SSLEngine/SSLSocketSSLEngine test templates [v4]

[Matthew Donovan]

> * Refactored SSLContextTemplate and SSLSocketTemplate to put common code in one base class (SSLContextTemplate)
> * Updated TLS/SSL tests to extend SSLSocketTemplate where possible.
> * Updated SSLEngineTemplate to accommodate changes in SSLContextTemplate. To keep this changeset to a reasonable size, updates to SSLEngine tests will be made under JDK-8301194.

Matthew Donovan has updated the pull request incrementally with one additional commit since the last revision:

  removed last use of MyX509ExtendedKeyManager in ALPN directory

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Changes:
  - all: https://git.openjdk.org/jdk/pull/12555/files
  - new: https://git.openjdk.org/jdk/pull/12555/files/3e971cc0..04d97ed7

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12555&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12555&range=02-03

  Stats: 142 lines in 2 files changed: 0 ins; 139 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/12555.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12555/head:pull/12555

PR: https://git.openjdk.org/jdk/pull/12555