[foreign-memaccess+abi] RFR: 8293400: Modify static constructors in MemorySegment [v4]

[Per Minborg]

> This PR changes the `MemorySegment` static constructors to be more like the one of `ByteBuffer`.

Per Minborg has updated the pull request incrementally with one additional commit since the last revision:

  Fix JavaDocs in MemorySegment

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/718/files
  - new: https://git.openjdk.org/panama-foreign/pull/718/files/95229c63..a45833be

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=718&range=03
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=718&range=02-03

  Stats: 16 lines in 1 file changed: 8 ins; 1 del; 7 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/718.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/718/head:pull/718

PR: https://git.openjdk.org/panama-foreign/pull/718