Use truncation instead of rounding for big.Int division

[SupunS]

Fix #4172

Implements FLIP: onflow/flips#344

Description

Use truncation division (big.Int.Quo()) instead of rounding, for number types backed by big.Int, to be consistent with the rest of the number types that are backed by Go's primitive values.

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• Targeted PR against master branch
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work
• Code follows the standards mentioned here
• Updated relevant documentation
• Re-reviewed Files changed in the Github PR explorer
• Added appropriate labels

[github-actions]

Cadence Benchstat comparison

This branch with compared with the base branch onflow:master commit 26e0f76
The command for i in {1..N}; do go test ./... -run=XXX -bench=. -benchmem -shuffle=on; done was used.
Bench tests were run a total of 7 times on each branch.

Collapsed results for better readability

[turbolent]

Nice!

[SupunS]

Going to merge this PR, so that we can get a preview release (and then a CLI build) out for people to test the new behaviour.

Merging the implementation doesn't mean this change is final, but rather is still very much subject to the outcome of the FLIP onflow/flips#344. If the sentiment is not positive on the FLIP, we can revert the PR. It's much more easier to revert, than having to manage separate branches for all the downstream dependencies needed for the CLI preview release.