chore: Move BigNumber.js to dependencies

[FrederikBolding]

Explanation

Since bignumber.js is used for typing in controller-utils, it should likely be a dependency to prevent issues when building with TS downstream.

There is probably a larger conversation to have here about when to use types as devDeps and when to use them as deps, but in our architecture today we rely heavily on all types to be included as dependencies. This causes a lot of potentially avoidable dependency management.

Changelog

@metamask/controller-utils

• Fixed: Move bignumber.js to dependencies

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've highlighted breaking changes using the "BREAKING" category above as appropriate
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes