[jdk17u-dev] RFR: 8309667: TLS handshake fails because of ConcurrentModificationException in PKCS12KeyStore.engineGetEntry

[Goetz Lindenmaier]

I backport this for parity with 17.0.19-oracle.

Needed to resolve PKCS12KeyStore.java. Omitted one chunk in PKCS12KeyStore.java because engineGetAttributes() which should be edited is not in 17.  It was added in 18 by [8225181](https://bugs.openjdk.org/browse/JDK-8225181) KeyStore should have a getAttributes method

I had to adapt the tests becasue there are no virtual threads and especially because 
https://bugs.openjdk.org/browse/JDK-8225181: "KeyStore should have a getAttributes method" is missing.

 SAP nightly testing passed.

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Commit messages:
 - Adapt test coding to Java 17
 - backport d2e2c4cef1f15a3fc7f1f619470d23ae6bb37725

Changes: https://git.openjdk.org/jdk17u-dev/pull/4240/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=4240&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8309667
  Stats: 269 lines in 3 files changed: 262 ins; 2 del; 5 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/4240.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/4240/head:pull/4240

PR: https://git.openjdk.org/jdk17u-dev/pull/4240