Gate MANAGE_KEY_GESTURES protection level change with a flag

A new flag is introduced because flags used for resources gating must be read only flags.

Flag: com.android.window.flags.grant_manage_key_gestures_to_recents
Bug: 406452076
Bug: 412920984
Test: atest CtsPermissionPolicyTestCases
Change-Id: Ic7c9e4c552e40da1b7f066570733b474e82471fc