gh-153437: Make pegen output error detection checks after loop body for '*' rules.

[stestagg]

Currently, the pegen output produces this for '+' rules after the children have been parsed:

    if (_n == 0 || p->error_indicator) {
        PyMem_Free(_children);
        p->level--;
        return NULL;
    }

But for '*' rules, no check is done at all, (skipping the _n == 0 makes sesnse of course)

For '*' it's possible for an error to be raised when parsing children, and currently the parser sets the error flag/exception but does not return NULL, so parent rules might not detect the error appropriately, as in this code:

    if (
        (a = _PyPegen_expect_token(p, FSTRING_START))  // token='FSTRING_START'
        &&
        (b = _loop0_79_rule(p))  // fstring_middle*
        &&
        (c = _PyPegen_expect_token(p, FSTRING_END))  // token='FSTRING_END'
    )

In this example, _PyPegen_expect_token can raise a SyntaxWarning which trips a debug assert.

This change outputs the same p->error_indicator check for '*' rules as for '+' rules.

Note, there are lots of rules affected by this change, but it seems to me that this is a latent bug for each of them, even though it might not be possible to trigger an error for all of them.

• Issue: Compiling code that mixes: deeply nested brackets and invalid escapes in f-strings causes debug assert/abort #153437

[stestagg]

Duplicate of #150067