[foreign-memaccess+abi] RFR: 8277945: Use snippets in jdk.incubator.foreign API documentation [v2]

[Julia Boes]

> This change replaces `<pre>{@code ...}</pre>` blocks with the new `@snippet` tag.

Julia Boes has updated the pull request incrementally with one additional commit since the last revision:

  revert non Java snippets

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

Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/621/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/621/files/78313ef0..fde32562

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=621&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=621&range=00-01

  Stats: 15 lines in 2 files changed: 2 ins; 1 del; 12 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/621.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/621/head:pull/621

PR: https://git.openjdk.java.net/panama-foreign/pull/621