seq: add a lower bound for exponents

[alexs-sh]

About

This PR adds a lower bound for the minimum exponent value to prevent overflow when parsing BigDecimal numbers.

Before

cargo run -- seq 1e-9223372036854775808
seq: invalid floating point argument: '1e-9223372036854775808'

After

cargo run -- seq 1e-9223372036854775808

Expected

seq 1e-9223372036854775808

Thank you

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/misc/stdbuf. tests/misc/stdbuf is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)
Congrats! The gnu test tests/seq/seq-precision is no longer failing!

[sylvestre]

Congrats! The gnu test tests/seq/seq-precision is no longer failing!

Excellent!