refactor: add evm amount calculation for tss migration

[kingpinXD]

Description

• Adds amount calculation into the TSS migration function

Closes: #1620

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)
• This change requires a documentation update

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Include instructions and any relevant details so others can reproduce.

• Tested CCTX in localnet
• Tested in development environment
• Go unit tests
• Go integration tests
• Tested via GitHub Actions

Checklist:

• I have added unit tests that prove my fix feature works

[github-actions]

!!!WARNING!!!
nosec detected in the following files: zetaclient/evm_signer.go

Be very careful about using #nosec in code. It can be a quick way to suppress security warnings and move forward with development, it should be employed with caution. Suppressing warnings with #nosec can hide potentially serious vulnerabilities. Only use #nosec when you're absolutely certain that the security issue is either a false positive or has been mitigated in another way.

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Broad #nosec annotations should be avoided, as they can hide other vulnerabilities. The CI will block you from merging this PR until you remove #nosec annotations that do not target specific rules.

Pay extra attention to the way #nosec is being used in the files listed above.

[ws4charlie]

looks good, left minor comment, no blocking