Fix LOAD_COMMON_CONSTANT argrepr behavior on 3.15

[Quinntyx]

On 3.15, argrepr in dis has been adjusted to the actual LOAD_COMMON_CONSTANT values, unlike 3.14 where they are still integers. This causes a parity mismatch between xdis and dis on 3.15.

This PR fixes this parity issue by adding a hook in bytecode.py and updating opcode_315.py to use LOAD_COMMON_CONSTANT values for argval, and changing argrepr to use repr(argval) to avoid the need for 2 LOAD_COMMON_CONSTANT tables.

Issue reproduction

import dis
import sys
from xdis import Bytecode, get_opcode

code = compile(
    'result = {"success": True, "failure": False}',
    "<test>",
    "exec",
)

native = [
    (inst.arg, inst.argval, inst.argrepr)
    for inst in dis.get_instructions(code)
    if inst.opname == "LOAD_COMMON_CONSTANT"
]
cross = [
    (inst.arg, inst.argval, inst.argrepr)
    for inst in Bytecode(code, get_opcode(sys.version_info[:2], False))
    if inst.opname == "LOAD_COMMON_CONSTANT"
]

print("dis:", native)
print("xdis:", cross)

Output on 3.15:

dis:  [(9, True, 'True'), (10, False, 'False'), (7, None, 'None')]
xdis: [(9, 9, 'True'), (10, 10, 'False'), (7, 7, 'None')]

[rocky]

This is apparently a recent addition to Python 3.15. I am not seeing it in 3.15.0a7.

LGTM though. Verified on 3.15.0b3.

[rocky]

BTW. Unrelated. The other day I was listing 3.14 instructions, and I see that disassembly is not showing the argument value on a STORE_FAST. Something I'll look at when I get a chance.