RFR: 8373538: Migrate all tests to null-safe "SimpleSSLContext" methods [v2]

[Volkan Yazici]

> 1. [JDK-8372661] introduced null-safe static factory methods to `SimpleSSLContext`
> 2. [JDK-8373515] migrated `test/jdk/java/net/httpclient/` to these new methods
> 3. [JDK-8373537] migrated `test/jdk/com/sun/net/httpserver/` to these new methods
> 4. This PR migrates all remaining `SimpleSSLContext` usages, *and* removes nullable `SimpleSSLContext` factory methods
> 
> [JDK-8372661]: https://bugs.openjdk.org/browse/JDK-8372661
> [JDK-8373515]: https://bugs.openjdk.org/browse/JDK-8373515
> [JDK-8373537]: https://bugs.openjdk.org/browse/JDK-8373537

Volkan Yazici has updated the pull request incrementally with one additional commit since the last revision:

  Remove wildcard imports

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28905/files
  - new: https://git.openjdk.org/jdk/pull/28905/files/ad954627..fced195e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28905&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28905&range=00-01

  Stats: 8 lines in 1 file changed: 4 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/28905.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28905/head:pull/28905

PR: https://git.openjdk.org/jdk/pull/28905