[foreign-memaccess] RFR: 8253355: Add some overloads to memory access API [v2]

[Maurizio Cimadamore]

> This patch adds two overload:
> 
> * MemoryAddress::asSegmentRestricted which takes an Object attachment
> * MemorySegment::asSlice which takes a MemoryAddress base and a new length
> 
> These overloads make the API slightly more usable.

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Address review comments
  Fix impl issue with attachment not being propagated

-------------

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/341/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/341/files/dc027094..c959b0dd

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=341&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=341&range=00-01

  Stats: 15 lines in 2 files changed: 10 ins; 0 del; 5 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/341.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/341/head:pull/341

PR: https://git.openjdk.java.net/panama-foreign/pull/341