DurationFormatter: Duration Formatter Digital Implementation

[kartva]

Blocked on merging #5208

[sffc]

Really good start!

[younies]

Good start, send the piece of code for decimal.rs in a different PR and lets discuss this PR today

[younies]

Fix CLI

[sffc]

Approved but I agree it would be nice to pull the fixed_decimal change into its own PR that lands before this one

[kartva]

Filed #5319 for fixed_decimal bug fix, and reverted the change in this PR.

[younies]

in a following PR:

Suggested change

	impl DurationSign {
	pub(crate) fn as_fixed_decimal_sign(&self) -> fixed_decimal::Sign {
	match self {
	DurationSign::Positive => fixed_decimal::Sign::Positive,
	DurationSign::Negative => fixed_decimal::Sign::Negative,
	}
	}
	}
	impl As<fixed_decimal::Sign> for DurationSign {
	fn as(&self) -> Sign {
	match self {
	DurationSign::Positive => fixed_decimal::Sign::Positive,
	DurationSign::Negative => fixed_decimal::Sign::Negative,
	}
	}
	}