[TASK] Remove old class files from ext:openid

Removes old class files from ext:openid except the two
current entry points for _eid and _return.

Change-Id: Ibdeca07881aad92af28c9f0e81c42a4ee1b600c2
Resolves: #55808
Related: #47756
Releases: 6.2
Reviewed-on: https://review.typo3.org/27507
Reviewed-by: Oliver Klee
Reviewed-by: Marcin Sągol
Reviewed-by: Anja Leichsenring
Tested-by: Anja Leichsenring