feat(sia): transaction serde

[Alrighttt]

Serde Changes

• Separated Specifier to distinct module
• v2 transaction creation and encoding support is functional except FileContractResolution.
• Transaction signing demonstrated in unit tests.
• Force explicit choice of encoding version and better memory structuring for Version types- re: @mariocynicys's feedback on PR https://github.com/KomodoPlatform/komodo-defi-framework/pull/2108

API Changes

• Added more verbose errors to fetch_and_parse function.
• Separated endpoints to distinct module.
• Added api/addresses/:address/outputs/siacoin endpoint
• Parse to URL instead of String and improve parse errors.

Refactoring and Cleanup

• Miscellaneous refactoring and cleanup.
• Fix and format multiple modules and unit tests.

There are many placeholders and TODOs still included in this pull request. Ready for review, but these sections of code are subject to change.

The next steps are to reorganize all the Sia code into a distinct "Sia Rust" crate. All DeFi framework logic will be separated.