[foreign-memaccess+abi] RFR: Split long throws clauses in `MemorySegment` javadoc

[Maurizio Cimadamore]

As the title says, this PR applies some cleanup to the memory segment javadoc.

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Commit messages:
 - Initial push

Changes: https://git.openjdk.org/panama-foreign/pull/880/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=880&range=00
  Stats: 41 lines in 1 file changed: 3 ins; 0 del; 38 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/880.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign.git pull/880/head:pull/880

PR: https://git.openjdk.org/panama-foreign/pull/880