Handle with token with large number

[ryutamago]

Handle token with large number

There was a bug where the app didn't handle sending token with large number (1e21+)
This was due to how the BigNumber uses scientific notation for stringifying large number, we need to use toFixed method instead of toString method to avoid the scientific notation.

Types of changes

• Bugfix
• New feature
• Refactor
• Breaking change
• UI fix

Steps to reproduce

log in with a fake account tz1Y8cACwiwQYwLNzzHnBvLQBendT6DUR3Rn and try and send over 1000 of PLY token. This used to fail due to the string conversion with scientific notation.

Screenshots

Large number:

Before	Now
https://github.com/trilitech/umami-v2/assets/128799322/e0607670-25fd-4d9b-a36c-9eec25866cb1	https://github.com/trilitech/umami-v2/assets/128799322/4d6f8301-a6db-4057-a22f-466f31fff66c

I also checked with small number and that worked fine:

Screen.Recording.2023-09-29.at.16.47.50.mov

Checklist

• Tests that prove my fix is effective or that my feature works have been added
• Documentation has been added (if appropriate)
• Screenshots are added (if any UI changes have been made)
• All TODOs have a corresponding task created (and the link is attached to it)