Always expand tabs to four spaces in diagnostics (#19618)
## Summary
I was a bit stuck on some snapshot differences I was seeing in #19415,
but @BurntSushi pointed out that `annotate-snippets` already normalizes
tabs on its own, which was very helpful! Instead of applying this change
directly to the other branch, I wanted to try applying it in
`ruff_linter` first. This should very slightly reduce the number of
changes in #19415 proper.
It looks like `annotate-snippets` always expands a tab to four spaces,
whereas I think we were aligning to tab stops:
```diff
6 | spam(ham[1], { eggs: 2})
7 | #: E201:1:6
- 8 | spam( ham[1], {eggs: 2})
- | ^^^ E201
+ 8 | spam( ham[1], {eggs: 2})
+ | ^^^^ E201
```
```diff
61 | #: E203:2:15 E702:2:16
62 | if x == 4:
-63 | print(x, y) ; x, y = y, x
- | ^ E203
+63 | print(x, y) ; x, y = y, x
+ | ^^^^ E203
```
```diff
E27.py:15:6: E271 [*] Multiple spaces after keyword
|
-13 | True and False
+13 | True and False
14 | #: E271
15 | a and b
| ^^ E271
```
I don't think this is too bad and has the major benefit of allowing us
to pass the non-tab-expanded range to `annotate-snippets` in #19415,
where it's also displayed in the header. Ruff doesn't have this problem
currently because it uses its own concise diagnostic output as the
header for full diagnostics, where the pre-expansion range is used
directly.
## Test Plan
Existing tests with a few snapshot updates
