[vector-unstable] RFR: Merge panama-vector:master

[Sandhya Viswanathan]

Merge panama-vector:master

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Commit messages:
 - Merge
 - 8254311: Incorrect statements in createWindowsDevkit2017.sh
 - 8251861: Remove unused jdk.internal.ref.SoftCleanable and WeakCleanable
 - 8254704: Add missing @since tag to BodyPublishers::concat
 - 8254627: Cleanup {Abstract,Single,Split}IndexWriter classes
 - 8254672: ZGC: ZParallelOopsDo/ZSerialWeakOopsDo should use atomic load/store
 - 8229867: Re-examine synchronization usages in http and https protocol handlers
 - 8254671: ZGC: Remove unused roots iterator types
 - 8254177: (tz) Upgrade time-zone data to tzdata2020b
 - 8254576: ZGC: Clean up timers in roots iterators
 - ... and 335 more: https://git.openjdk.java.net/panama-vector/compare/fb1b6534...608b38b5

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - vector-unstable: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=10&range=00.0
 - panama-vector:master: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=10&range=00.1

Changes: https://git.openjdk.java.net/panama-vector/pull/10/files
  Stats: 92082 lines in 3292 files changed: 37172 ins; 39995 del; 14915 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/10.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/10/head:pull/10

PR: https://git.openjdk.java.net/panama-vector/pull/10