.mpy files store multiple copies of identifiers #3054
Description
There's something wrong with .mpy files: they store the string value of source filename again and again, multiple times:
./lib/time.py.ustruct.unpack
@iiiiiiiii.tuple...tmg.............&G(0((+......7......d.......d.............Q.f.......d...h...d..........d.........X.!...d.[.strftime
./lib/time.py.time.int.array.array.i
localtime_ bytearray strftime_.str.utf-8...format.tR............)&G(.(......7......d.......d.............f.......d...
...........f.d.[ localtime
./lib/time.py.time.int.ustruct.pack.i
localtime_._c_tm_to_tuple.uctypes.bytearray_at...tR............3&G(.(......7......d.......d.............f.......d...
...........f.d.[.gmtime
./lib/time.py.time.int.ustruct.pack.i.gmtime_._c_tm_to_tuple.uctypes.bytearray_at...t....... ....=........
...d.d.[.mktime
./lib/time.py.mktime_._tuple_to_c_tm...tt....... .....A.......d.[.perf_counter
./lib/time.py.time......... .....D.......d.[.process_time
./lib/time.py.clock..
That certainly doesn't help to save heap size when loading them.