Report precise location for invalid conversion flag

[dhruvmanila]

Summary

This PR updates the parser definition to use the precise location when reporting
an invalid f-string conversion flag error.

Taking the following example code:

f"{foo!x}"

On earlier version,

Error: f-string: invalid conversion character at byte offset 6

Now,

Error: f-string: invalid conversion character at byte offset 7

This becomes more useful when there's whitespace between ! and the flag value
although that is not valid but we can't detect that now.

Test Plan

As mentioned above.

[dhruvmanila]

Current dependencies on/for this PR:

• main
  • PR Report precise location for invalid conversion flag #7809 👈

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[codspeed-hq]

CodSpeed Performance Report

Merging #7809 will degrade performances by 2.5%

_{Comparing dhruv/conversion-flag-loc (dc9270b) with main (a1509df)}

Summary

❌ 1 regressions
✅ 24 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	dhruv/conversion-flag-loc	Change
❌	linter/default-rules[pydantic/types.py]	38 ms	39 ms	-2.5%

[github-actions]

PR Check Results

Ecosystem

✅ ecosystem check detected no changes.