[analyzer] Avoid unnecessary super region invalidation in `CStringChecker` (#146212)

Bounded string functions takes smallest of two values as it's copy size
(`amountCopied` variable in `evalStrcpyCommon`), and it's used to
decided whether this operation will cause out-of-bound access and
invalidate it's super region if it does.

for `strlcat`: `amountCopied = min (size - dstLen - 1 , srcLen)`
for others: `amountCopied = min (srcLen, size)`

Currently when one of two values is unknown or `SValBuilder` can't
decide which one is smaller, `amountCopied` will remain `UnknownVal`,
which will invalidate copy destination's super region unconditionally.

This patch add check to see if one of these two values is definitely
in-bound, if so `amountCopied` has to be in-bound too, because it‘s less
than or equal to them, we can avoid the invalidation of super region and
some related false positives in this situation.

Note: This patch uses `size` as an approximation of `size - dstLen - 1`
in `strlcat` case because currently analyzer doesn't handle complex
expressions like this very well.

Closes #143807.