gh-140256: Populate argrepr for LOAD_SMALL_INT

[davep]

Closes #140256.

• Issue: LOAD_SMALL_INT has empty argrepr via Bytecode #140256

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[sergey-miryanov]

Code looks good to me.
cc @markshannon @JelleZijlstra

[efimov-mikhail]

This fix looks correct, but I doubt about the need of two always equal values in this case.

[davep]

@efimov-mikhail Are you referring to the output of dis.dis here? Would that now ideally be changed as part of this PR?

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[efimov-mikhail]

Maybe we could add something like this if instr.argrepr and instr.argrepr != str(instr.arg)
to Formatter.print_instruction_line. But I want to hear another opinions.