[foreign-memaccess+abi] RFR: Remove specialized zero-lenght mapped segment

[Maurizio Cimadamore]

On Tue, 14 Feb 2023 15:37:49 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> This PR proposes to remove the specialized zero-length MappedMemorySegment.

Looks good - thx for beefing up the test!

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Marked as reviewed by mcimadamore (Committer).

PR: https://git.openjdk.org/panama-foreign/pull/793