Revert "Migrate eth-json-rpc-provider into core monorepo (1/2)" (#1753)

Reverts #1737

- The intention for this PR was to preserve the full git history of the
original repo, which means the commits shouldn't have been squashed
while merging.
- #1737 will be re-merged using the `--no-ff` option, which will be
temporarily enabled by admin.

Author: MajorLift