[clang] [analyzer] Add option assume-at-least-one-iteration (PR #125494)

[Donát Nagy via cfe-commits]

NagyDonat wrote:

I updated the name of the option and tried to clarify the comments that describe the relationship with `eagerly-assume` (but it's just a mostly-theoretical buggy corner case, so I wouldn't put it into the minimal two-sentence documentation).

@gamesh411 @steakhal Are you satisfied with this?

https://github.com/llvm/llvm-project/pull/125494