eth-json-rpc-provider migration - B1: Remove redundant files and di…

…rectories. (#1764)

## Explanation

This PR implements the following incremental step in the process for
migrating `eth-json-rpc-provider` into the core monorepo:

***

### Phase B: Staging in `migrated-packages/`
#### 1. Remove files and directories that will be replaced by
corresponding files in the monorepo root.
- [x] **Remove**: `.github/`, `.git*`, `scripts/`, `.depcheckrc.json`,
`.yarn/`, `.yarnrc.yml`, `yarn.lock`, `.editorconfig`, `.eslint*`,
`.prettier*`, `.nvm*`.
- [x] **Keep**: `src/`, `tests/`, `CHANGELOG.md`, `LICENSE`,
`package.json`, `README.md`, `jest.config.js`, `tsconfig*.json`,
`typedoc.json`.

***

See #1551 (comment)
for an outline of the entire process.

## Blocked by
- [x] #1790

## References

- Contributes to #1685
- Contributes to #1551

## Changelog

N/A

## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've highlighted breaking changes using the "BREAKING" category
above as appropriate