[foreign-memaccess+abi] RFR: 8291286: Improve JavaDocs for static constructors in MemorySession [v2]

[Per-Åke Minborg]

> This PR adds information to the static constructor methods in MemorySession to improve clarity for new users.
> 
> This is my first PR for a JDK project so I am eager to receive feedback and improvement suggestions from the community.

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

  Add @return tagg

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/693/files
  - new: https://git.openjdk.org/panama-foreign/pull/693/files/f5db97af..c0053b1d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=693&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=693&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 2 del; 1 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/693.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/693/head:pull/693

PR: https://git.openjdk.org/panama-foreign/pull/693