feat: added onBeforeSend hook to the connector interface

[petertonysmith94]

Relates to: FuelLabs/fuel-connectors#451

Summary

• Added onBeforeSend to the account sendTransaction method, to allow for altering of a transaction request before submission.
• Added onCustomFee to enable skipping "customFee" calculations in Fuel Wallet.

Checklist

• All changes are covered by tests (or not applicable)
• All changes are documented (or not applicable)
• I reviewed the entire PR myself (preferably, on GH UI)
• I described all Breaking Changes (or there's none)

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[github-actions]

This PR is published in NPM with version 0.0.0-pr-3487-20250109192939

[github-actions]

Coverage Report:

Lines	Branches	Functions	Statements
76.98%(+0.08%)	70.46%(+0.11%)	75.05%(+0.16%)	76.98%(+0.08%)

Changed Files:

Ok	File (✨=New File)	Lines	Branches	Functions	Statements
🔴	packages/account/src/account.ts	80.58% (+2.35%)	69.86% (+4.59%)	82.5% (+2.5%)	80.34% (+2.31%)
🔴	packages/account/src/connectors/fuel.ts	96.73% (+1.31%)	90.66% (+0%)	93.33% (+4.45%)	96.85% (+1.26%)