feat(currency): Add accounting formatting support to CurrencyFormatter<Compact>

[younies]

Summary

This PR implements accounting currency formatting support (e.g., formatting negative monetary values in parentheses like ($12K) in en-US) for compact currency formatting (CurrencyFormatter<Compact>).

This PR is stacked on top of #8182 (compact-currency-formatting).

Changelog

1. Restore CurrencyFormatterOptions & CurrencyUsage:

   • Restores CurrencyFormatterOptions in options.rs containing pub usage: CurrencyUsage.
   • Defines pub enum CurrencyUsage { #[default] Standard, Accounting }. (Note: Cash is left out of this PR intentionally so that this stack merges cleanly with feat(currency): Add accounting formatting and relax constructor validation #8177 when both reach upstream main).

2. Accounting Pattern Resolution in CurrencyFormatter<Compact>:

   • Updates try_new_short / try_new_narrow (and unstable/buffer counterparts) on CurrencyFormatter<Compact> to accept options: CurrencyFormatterOptions.
   • In format_fixed_decimal, checks self.options.usage == CurrencyUsage::Accounting. When formatting a negative number, queries accounting_negative_pattern() (or accounting_alpha_next_to_number_negative_pattern()) from CurrencyEssentialsV1, falling back cleanly to standard negative patterns if no accounting pattern is defined for the locale.
   • Sign Wrapping Prevention: When an accounting negative pattern is applied (which already formats the sign via parentheses or symbols), passes Sign::None to DecimalFormatter::format_sign so it does not prepend a redundant minus sign (preventing -($12K)).

3. Zero Conflicts with Standard Decimal Formatting (feat(currency): Add accounting formatting and relax constructor validation #8177):

   • Standard Decimal currency formatting (format.rs and formatter.rs constructor signatures) is kept 100% untouched to avoid merge conflicts with feat(currency): Add accounting formatting and relax constructor validation #8177.

4. Testing:

   • Updates existing short/narrow compact test callers in compact_format.rs to pass Default::default().
   • Adds a new test_accounting unit test in compact_format.rs verifying that CurrencyUsage::Accounting formats -12345.67 as ($12K) in en-US.

Verification

• cargo clippy -p icu_experimental --no-deps passed cleanly.
• cargo fmt --all -- --check passed cleanly.
• cargo test -p icu_experimental passed (all 49 unit tests and 40 doctests).

Fixes #8185

[robertbastian]

needs rebase