h265parser: Various fix for registered user data SEI handling
tests: h265parser: Add test for registered user data SEI
h265parser: Fix registered user data SEI leak
... and add fix for the SEI data in gst_h265_sei_copy()
h265parser: Do not allocate too large size of memory for registered user data SEI
Don't be confused by the unit of payload size (i.e., bits and bytes)
Also this need a documentation with Since mark