fix: fiat amount lps gas fee maths

[NeOMakinG]

Description

Inside the validation, we are taking the minimum dust threshold in account with the gas fees, but as a presentational value, we are only displaying the gas fees without the dust threshold

This PR does add the dust threshold to the gas amount to make sure what we display is equal to the actual security check

As a followup, we might want to bring back the 0.0001 dust threshold as written in the thorchain doc: https://dev.thorchain.org/saving-guide/quickstart-guide.html#basic-mechanics

Really low deposit could be not working anymore for BTC (under around 15$ deposits), but it would permit to withdraw from the BTC pool with a smaller amount

Issue (if applicable)

closes #7778

Risk

Low

High Risk PRs Require 2 approvals

What protocols, transaction types, wallets or contract interactions might be affected by this PR?

Testing

• Go to a sym BTC pool, try to withdraw sym
• The gas fee amount should reflect the price for the actual dust threshold (0.0003 BTC, which is around 18$ at the time of writing) + the gas fees

Engineering

n/a

Operations

n/a

• 🏁 My feature is behind a flag and doesn't require operations testing (yet)

Screenshots (if applicable)

For BTC, the gas fee was under 1$

Now

Other pools are sane, tested AVAX, COSMOS, FOX

[gomesalexandre]

Tested locally, confirmed current dust amount (0,0003 BTC i.e ~19 USD) is properly added and surfaced to users