[jdk25u-dev] RFR: 8372661: Add a null-safe static factory method to "jdk.test.lib.net.SimpleSSLContext"

[Roland Mesde]

Backporting JDK-8372661: Add a null-safe static factory method to "jdk.test.lib.net.SimpleSSLContext".

This PR introduces a new static factory method that returns a non-null SSLContext or throws an exception on failure.

For parity with Oracle JDK.

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=jdk_net

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Commit messages:
 - Backport 629e4ac6f45c87898f6a014f28a443c800413869

Changes: https://git.openjdk.org/jdk25u-dev/pull/210/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=210&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8372661
  Stats: 95 lines in 1 file changed: 51 ins; 5 del; 39 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/210.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/210/head:pull/210

PR: https://git.openjdk.org/jdk25u-dev/pull/210