ESQL: Fix ROUND() with unsigned longs throwing in some edge cases

[ivancea]

There were 3 error cases with ROUND(number, decimals):

• Decimals accepted unsigned longs, but threw a 500 with a can't process [unsigned_long -> long] in the cast evaluator
  • Fixed by improving the resolveType()
• If the number was a BigInteger unsigned long, there were 2 cases throwing an exception:
  1. Negative decimals outside the range of integer: Error
  2. Negative decimals insie the range of integer, but "big enough" for BigInteger.TEN.pow(...) to throw a BigInteger would overflow supported range

Also, when the number is a BigInteger and the decimals is a big negative (but not big enough to throw), it may be very slow. Taking many seconds for a single computation (It tries to calculate a 10^(big number). I didn't do anything here, but I wonder if we should limit it.
It's not an "error" in any case, so this PR is limited to the 500 errors.

[github-actions]

Documentation preview:

• ✨ Changed pages

[elasticsearchmachine]

Pinging @elastic/es-analytical-engine (Team:Analytics)

[elasticsearchmachine]

Hi @ivancea, I've created a changelog YAML for you.