feat: Shared currency and token formatters

[n3ps]

Explanation

This is a port of the new Intl.NumberFormat currency formatters from metamask-extension. Moving it a shared library so it can be consumed from both mobile and extension.

• What is the current state of things and why does it need to change?
  There is inconsistent and multiple one-off implementations for fiat currency and token formatting in the mobile and extension clients

• What is the solution your changes offer and how does it work?
  Create a shared set of formatters that aligns mobile and extension.

References

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 communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes

[mcmire]

Eventually it may be a good idea to move these over to the @metamask/utils repo, depending on where they are likely to be used.

That said for now this seems good.

[n3ps]

Eventually it may be a good idea to move these over to the @metamask/utils repo, depending on where they are likely to be used.

That said for now this seems good.

@mcmire Discussed this with Mark, I considered utils but the formats cater more closely with MetaMask's use cases

[mcmire]

@n3ps I see. Sounds good!