avcodec/parser: move parsers list and related API to its own file

And add it to the CONFIGURABLE_COMPONENTS list in Makefile. This way, changes
to the new file will be tracked and the usual warning to suggest re-running
configure will be shown.

Reviewed-by: Rostislav Pehlivanov <atomnuker@gmail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

Makefile

@@ -58,6 +58,7 @@ tools/target_dec_%_fuzzer$(EXESUF): $(FF_DEP_LIBS)
 CONFIGURABLE_COMPONENTS =                                           \
     $(wildcard $(FFLIBS:%=$(SRC_PATH)/lib%/all*.c))                 \
     $(SRC_PATH)/libavcodec/bitstream_filters.c                      \
+    $(SRC_PATH)/libavcodec/parsers.c                                \
     $(SRC_PATH)/libavformat/protocols.c                             \
 
 config.h: ffbuild/.config