[jdk11u-dev] RFR: 8301700: Increase the default TLS Diffie-Hellman group size from 1024-bit to 2048-bit

[Alexey Bakhtin]

Backport is almost clean.
The test is manually updated because of no JDK-8211018 in JDK11
CSR is approved for all major versions.
sun/security/ssl/DHKeyExchange tests passed

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Commit messages:
 - Backport 26b111d714c3ee62bd10a5e2ab44be01c13ff42e

Changes: https://git.openjdk.org/jdk11u-dev/pull/1835/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1835&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301700
  Stats: 30 lines in 2 files changed: 1 ins; 10 del; 19 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1835.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/1835/head:pull/1835

PR: https://git.openjdk.org/jdk11u-dev/pull/1835