## Explanation

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Improves error handling in the RPC service by making it more specific
and consistent. The changes include:

- Clarifies error handling for different HTTP status codes:
  - 401: Unauthorized error
  - 402/404/5xx: Resource unavailable error
  - 405/501: Method not found error
  - 429: Rate limiting error
  - Other 4xx: Invalid request error
  - Invalid JSON: Parse error

## References

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Fixes #5844

## Changelog

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## 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](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [ ] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes