[foreign-memaccess+abi] RFR: 8274219: Add back generic factory to create value layouts [v2]

[Maurizio Cimadamore]

> This patch adds back a factory to create value layouts in a generic way. While we cannot make the API 100% type safe, some dynamic usages can greatly benefit from this. The `Binding` class provides a good example (greatly simplified here). Also, the logic for reconstructing layouts (see `describeConstable`) becomes a lot more regular.

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

  Update src/jdk.incubator.foreign/share/classes/jdk/incubator/foreign/MemoryLayout.java
  
  Co-authored-by: Paul Sandoz <paul.d.sandoz at googlemail.com>

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/579/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/579/files/6c477aed..75631014

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=579&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=579&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/579.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/579/head:pull/579

PR: https://git.openjdk.java.net/panama-foreign/pull/579