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

[Per Minborg]

On Wed, 9 Nov 2022 09:49:14 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> 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>

These changes will be made through PR_20 instead.

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

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