[foreign-memaccess+abi] RFR: 8303666: Move address layout outside of ValueLayout namespace [v2]

[Maurizio Cimadamore]

> This patch moves ValueLayout.OfAddress into a toplevel class. This seems desirable since address layouts are very important in the FFM API, and also provides seadditional methods on top of `ValueLayout` to get/set a *target layout*.

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

  Add copyright header

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/811/files
  - new: https://git.openjdk.org/panama-foreign/pull/811/files/13e321d1..96ecbae1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=811&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=811&range=00-01

  Stats: 26 lines in 1 file changed: 26 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/811.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/811/head:pull/811

PR: https://git.openjdk.org/panama-foreign/pull/811