[jdk11u-dev] RFR: 8023980: JCE doesn't provide any class to handle RSA private key in PKCS#1

[Goetz Lindenmaier]

I backport this for parity with 11.0.20-oracle.

I had to resolve RSAPrivateCrtKeyImpl.java.
Besides context, newKey() is refactored in 11 because
8271199: Mutual TLS handshake fails signing client certificate with c...
is already backported.

TestKeyFactory.java
manual resolve. Some of the edits are already there (in testPrivate()).
They probably came with 8254717.

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Commit messages:
 - Backport 68cf65d284a73f5c5229d30ca642bba9585095f3

Changes: https://git.openjdk.org/jdk11u-dev/pull/1946/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1946&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8023980
  Stats: 447 lines in 6 files changed: 298 ins; 52 del; 97 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1946.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/1946/head:pull/1946

PR: https://git.openjdk.org/jdk11u-dev/pull/1946