[foreign-memaccess+abi] RFR: 8292174: Add unaligned layouts to ValueLayout [v6]

[Per Minborg]

> The layouts are placed in a special `Unaligned` class. This prevents the classes to be seen on the top level (for less cluttering) and allows lazy initialization of items that are likely not so much used.

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

  Change unaligned init code

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Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/705/files
  - new: https://git.openjdk.org/panama-foreign/pull/705/files/ab34e8a0..4fc3d162

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=705&range=05
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=705&range=04-05

  Stats: 12 lines in 1 file changed: 0 ins; 5 del; 7 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/705.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/705/head:pull/705

PR: https://git.openjdk.org/panama-foreign/pull/705