[foreign-memaccess+abi] RFR: Add @apiNote to package-info [v2]

[Per Minborg]

> This PR proposes an additional `@apiNote` saying native memory behaves differently that normal Java objects.

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

  Update src/java.base/share/classes/java/lang/foreign/package-info.java
  
  Co-authored-by: Maurizio Cimadamore <54672762+mcimadamore at users.noreply.github.com>

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

Changes:
  - all: https://git.openjdk.org/panama-foreign/pull/751/files
  - new: https://git.openjdk.org/panama-foreign/pull/751/files/4c4928d6..4661d30b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=panama-foreign&pr=751&range=01
 - incr: https://webrevs.openjdk.org/?repo=panama-foreign&pr=751&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/751.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/751/head:pull/751

PR: https://git.openjdk.org/panama-foreign/pull/751