Patch adds required functionality for extension to manage a list of
application provided callbacks and handle debug reporting from driver
and application side.

v2: remove useless helper anv_debug_report_call
    add locking around callbacks list
    use vk_alloc2, vk_free2
    refactor CreateDebugReportCallbackEXT
    fix bugs found with crucible testing

v3: provide ANV_FROM_HANDLE and use it
    misc fixes for issues Jason found
    use vk_find_struct_const for finding ctor_cb

Signed-off-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>