chore: clean-up Multichain API errors

[wenfix]

Explanation

Currently, on Multichain API handlers (@metamask/multichain-api-middleware), we're throwing a JSON-RPC Internal Error (-32603) instead of CAIP-25 5000. We're also inling errors instead of using those defined in Caip25Errors. This PR adds missing errors and updates usage across handlers.

References

Fixes https://github.com/MetaMask/MetaMask-planning/issues/5251

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