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

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Sirraide wrote:

> 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

I mean, at that point we might want to consider printing like 2.89e76 or sth like that, but I feel like most big numbers in diagnostics won’t be *that* big

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