Add swap simulating RPC

[gztensor]

Description

Two RPC calls were added:

• swapRuntimeApi::simSwapTaoForAlpha
• swapRuntimeApi::simSwapAlphaForTao

The return value is SwapResult struct:

pub struct SimSwapResult {
    pub tao_amount: TaoCurrency,
    pub alpha_amount: AlphaCurrency,
    pub tao_fee: TaoCurrency,
    pub alpha_fee: AlphaCurrency,
}

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Other (please describe):

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have run cargo fmt and cargo clippy to ensure my code is formatted and linted correctly
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Screenshots (if applicable)

[ales-otf]

hi Greg! could you, please, take a look at my comments?

[RyanZhuu]

Can the websites in the Screenshots be accessed? Could you please provide the URLs?