[clang] [Clang] Add thousands-separator to "cannot allocate array; evaluated array bound [...] exceeds the limit" diagnostic (PR #211785)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

It's hard to say whether this improves the diagnostic or not, tbh!

Before:
```
value 28948022309329048855892746252171976962977213799489202546401021394546514198529 is outside the range of representable
```
After:
```
value 28'948'022'309'329'048'855'892'746'252'171'976'962'977'213'799'489'202'546'401'021'394'546'514'198'529 is outside the range of representable
```
I don't think either is readable. :-D

There are some other interesting cases in the failures, the one that I think is most interesting would be when trying to display values that encode a date. e.g., `20260728` turns into `20'260'728` when it could actually be easier to read as `2026'07'28`. Not certain we want to get clever here though, but it is worth thinking about.

https://github.com/llvm/llvm-project/pull/211785