[Seq] Fix rewrite of `(seq.nth s n)` for large `n` (#8083)

[Seq] Fix rewrite of `(seq.nth s n)` for large `n` (#8083)

When rewriting (seq.nth s n) where both terms are constants, cvc5 was
blindly converting the n to a uint32_t, which caused issues when n
was greater than the largest value that can be represented by a 32-bit
integer. This commit introduces a corresponding check and does not
perform the rewrite for large n.