py/persistentcode: Remove remaining native qstr linking support.

Support for architecture-specific qstr linking was removed in
d4d53e9e11, where native code was changed to
access qstr values via qstr_table.  The only remaining use for the special
qstr link table in persistentcode.c is to support native module written in
C, linked via mpy_ld.py.  But native modules can also use the standard
module-level qstr_table (and obj_table) which was introduced in the .mpy
file reworking in f2040bfc7e.

This commit removes the remaining native qstr liking support in
persistentcode.c's load_raw_code function, and adds two new relocation
options for constants.qstr_table and constants.obj_table.  mpy_ld.py is
updated to use these relocations options instead of the native qstr link
table.

Signed-off-by: Damien George <damien@micropython.org>

tools/mpy-tool.py

@@ -976,7 +976,6 @@ class RawCodeNative(RawCode):
         kind,
         fun_data,
         prelude_offset,
-        qstr_links,
         scope_flags,
         n_pos_args,
         type_sig,
@@ -989,7 +988,6 @@ class RawCodeNative(RawCode):
             self.scope_flags = scope_flags
             self.n_pos_args = n_pos_args
 
-        self.qstr_links = qstr_links
         self.type_sig = type_sig
         if config.native_arch in (
             MP_NATIVE_ARCH_X86,
@@ -1196,15 +1194,6 @@ def read_raw_code(reader, cm_escaped_name, qstr_table, obj_table, segments):
         rc = RawCodeBytecode(cm_escaped_name, qstr_table, obj_table, fun_data)
     else:
         # Create native raw code.
-        qstr_links = []
-        if kind in (MP_CODE_NATIVE_PY, MP_CODE_NATIVE_VIPER):
-            # Read qstr link table.
-            n_qstr_link = reader.read_uint()
-            for _ in range(n_qstr_link):
-                off = reader.read_uint()
-                qst = read_qstr(reader, segments)
-                qstr_links.append((off >> 2, off & 3, qst))
-
         native_scope_flags = 0
         native_n_pos_args = 0
         native_type_sig = 0
@@ -1242,7 +1231,6 @@ def read_raw_code(reader, cm_escaped_name, qstr_table, obj_table, segments):
             kind,
             fun_data,
             prelude_offset,
-            qstr_links,
             native_scope_flags,
             native_n_pos_args,
             native_type_sig,