With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

Backport of elastic#121747 to 8.x

This test creates an incorrectly-serialized handshake which cannot be
validated, and elastic#121747 made that validation compulsory. This test
corrects the serialization.

Closes 121816

This test creates an incorrectly-serialized handshake which cannot be
validated, and elastic#121747 made that validation compulsory. This test
corrects the serialization.

Closes elastic#121816

This test creates an incorrectly-serialized handshake which cannot be
validated, and #121747 made that validation compulsory. This test
corrects the serialization.

Closes #121816

This test creates an incorrectly-serialized handshake which cannot be
validated, and #121747 made that validation compulsory. This test
corrects the serialization.

Closes #121816

This test creates an incorrectly-serialized handshake which cannot be
validated, and #121747 made that validation compulsory. This test
corrects the serialization.

Closes #121816

This test creates an incorrectly-serialized handshake which cannot be
validated, and #121747 made that validation compulsory. This test
corrects the serialization.

Closes #121816

)

* Validate transport handshake from known version (#121747)

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

* Fix version/transportversion confusion

* CI poke

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

Backport of #121747 to 8.x

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

Backport of elastic#121747 to 8.x

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

Backport of elastic#121747/elastic#121802 to 8.18

With parallel releases on multiple branches it's possible that an older
branch sees a transport version update that is not known to a
numerically newer but chronologically older version. In that case the
two nodes cannot intercommunicate, so with this commit we reject such
connection attempts at the version negotiation stage.

Backport of #121747 to 8.x