SCRIPTS: improve announce-release to support different tag and versions

SCRIPTS: improve announce-release to support different tag and versions

By having three variables it will be easier to preset the version and
the tag separately. One contains the announced version, another one the
associated tag and the last one the final commit ID (used as the ending
point before the release). This initially allows to check for the HEAD
matching the tag only when the version was not forced, hence re-announce
already tagged versions after some extra commits were added for example.

(cherry picked from commit 0c612936b2f4319dcc55567af4aa425b1d6d52c7)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit d1754b6f0c0578569cf4673e01dfb547e2558bc3)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 64028f4e8f55c3734c35a4355ac5138b87290cf6)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>