Tier 1 code generator doesn't track used values if named unused

[markshannon]

Bug report

Bug description:

The _INIT_CALL_BOUND_METHOD_EXACT_ARGS uop definition requires explicit code to force the function and self to be written to memory, or the values are lost.
This is because following uops do not use those values, so when they are used they are loaded from memory.

This can be fixed in one of two ways:

• Raise an error if a value that is cached is marked as unused forcing it to be explicitly named.
• Implicitly name unused but cached values in the code generator, so that they are tracked properly.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• GH-121784: Generate an error during code gen if a variable is marked unused, but is used and thus cached in a prior uop. #121788

[markshannon]

I've opted for generating an error, rather than renaming the variable.
The fix is much simpler, and adding meaningful names is harmless at worse and can improve comprehension.