feat(cdk/a11y): add a TreeKeyManager, with next/prev implemented (#24659)

* feat(cdk/a11y): add API for TreeKeyManager

* feat(cdk/a11y): add activeItem into the TreeKeyManager

* feat(cdk/a11y): store the options into the key manager

* feat(cdk/a11y): add _getItems translation layer

* feat(cdk/a11y): add skeleton for keydown actions

* feat(cdk/a11y): implement activate item

* feat(cdk/a11y): implement various focus methods

* feat(cdk/a11y): implement onClick, remove lint disables

* feat(cdk/a11y): partial spec migration, fixed some bugs in impl

* fix(cdk/tree): fix lint errors

* fix(cdk/a11y): fix lint errors pt2

Author: BobobUnicorn