Borrow function inputs where possible

[dusan-maksimovic]

Description

This PR changes couple of function signatures in the code base that were taking ownership over Deps, Env, etc. to make them use borrowed values. This makes the code more composable, and these functions didn't even need to take ownership.
Also removed comments regarding rounding when converting Decimal to UInt128, since we already decided to do rounding to larger value.

The PR doesn't change the storage, nor the external API, just the internal functions.

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