Drupal 10 compatibility

Issue #3194579 by andypost, dench0, nguerrier: Use $form_state for re…

…trieving mail value in _sharedemail_form_submit function

Issue #3121118 by Neslee Canil Pinto: Replace deprecated method and C…

…ompatibility with Drupal 9

Added allowed duplicate email tests and updated schema config

Added allowed duplicate email tests and updated schema config

Added "create shared email account" permission and constraint

Issue #2717567 by burgdawg, Baik Ho, mmjvb, colan, aufumy: Drupal 8 v…

…ersion of Shared eMail

Issues #[1025840] by jjwhitney: Incompatible with email_registration …

…module

Issues #[896520] by Grayside, BTMash: Subuser integration.