py/profile: Remove the requirement to disable MICROPY_COMP_CONST.

The only reason that const had to be disabled was to make the test output
match CPython when const was involved.  Instead, this commit fixes the test
to handle the lines where const is used.

Also:
- remove the special handling for MICROPY_PERSISTENT_CODE_SAVE in
  unix/mpconfigport.h, and make this automatic.
- move the check for MICROPY_PERSISTENT_CODE_SAVE to where it's used (like
  we do for other similar checks) and add a comment explaining it.

This work was funded through GitHub Sponsors.

Signed-off-by: Jim Mussared <jim.mussared@gmail.com>

tests/misc/sys_settrace_features.py

@@ -67,6 +67,11 @@ def trace_tick_handler(frame, event, arg):
     if any(name in frame_name for name in to_ignore):
         return
 
+    # Lines 4,5,7 create the `const` lambda, and line `15` is a `_X = const()` which
+    # MicroPython will not see as it's optimised out.
+    if "sys_settrace_importme" in frame.f_code.co_filename and frame.f_lineno in (4, 5, 7, 15):
+        return trace_tick_handler
+
     print("### trace_handler::main event:", event)
     __prof__.trace_tick(frame, event, arg)
 

tests/misc/sys_settrace_subdir/sys_settrace_importme.py

@@ -3,12 +3,18 @@ print("Yep, I got imported.")
 try:
     x = const(1)
 except NameError:
-    print("const not defined")
+    # Either running on CPython or MICROPY_COMP_CONST disabled.
+    const = lambda x: x
 
-const = lambda x: x
 
+# No const optimisation.
 _CNT01 = "CONST01"
+
+# Const assigned to an underscore name. Invisible to MicroPython with
+# MICROPY_COMP_CONST enabled.
 _CNT02 = const(123)
+
+# Consts assigned to regular name, executed normally.
 A123 = const(123)
 a123 = const(123)