fdo#75757: remove inheritance to std::vector

This also fixes possible memory leaks of SfxAllEnumValue_Impl
which may occur in SfxAllEnumItem::RemoveValue() of the original
implementation.

Change-Id: I5f458c546575d9e1f88b1167ae561537963c7b95
Reviewed-on: https://gerrit.libreoffice.org/10167
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>