GH-106360: Support very basic superblock introspection

[markshannon]

Adds indexing and len() support to uop superblocks, such that this:

def testfunc(x):
    i = 0
    while i < x:
        i += 1

testfunc(100)

for offset in range(0, 100, 2):
    try:
        ex = _testinternalcapi.get_executor(testfunc.__code__, offset)
        break
    except ValueError:
        pass

for uop in ex:
    print(uop)

produces this

('SAVE_IP', 7)
('LOAD_FAST', 1)
('SAVE_IP', 8)
('LOAD_CONST', 2)
('SAVE_IP', 9)
('_GUARD_BOTH_INT', 13)
('_BINARY_OP_ADD_INT', 13)
('SAVE_IP', 11)
('STORE_FAST', 1)
('SAVE_IP', 12)
('LOAD_FAST', 1)
('LOAD_FAST', 0)
('SAVE_IP', 13)
('COMPARE_OP_INT', 18)
('SAVE_IP', 15)

• Issue: Add basic introspection, like str() for executors. #106360

[markshannon]

This PR also adds _PyOpcode_OpName and _PyOpcode_uop_name to non-debug builds because they are only a few Kbs of static data, and it is nice to be able to introspect things.

[gvanrossum]

This just needs a merge.

In the light of rising concerns over symbols starting with _Py still being public, maybe we should rename these or move the header file? These tables should be allowed to change on a whim.

[gvanrossum]

I think once you merge main you'll see that this is now called SAVE_IP.

[markshannon]

In the light of rising concerns over symbols starting with _Py still being public.

They aren't public though. We strip _Py symbols from the binary, unless they are marked with a PyAPI_FUNC or PyAPI_DATA macro.