Implement LoomProvider2 for /eth endpoint

[enlight]

We need to start migrating loom-js over to the /eth JSON-RPC interface. Soon it should be possible to send Ethereum txs to the /eth endpoint, at which point it'll be possible to use something like Metamask without a LoomProvider (just using web3). Nonce management is still going to be tricky though, the /eth endpoint will only support what is essentially the basic NonceTxMiddleware

loom-js/src/middleware/nonce-tx-middleware.ts

Line 21 in 3304853

export class NonceTxMiddleware implements ITxMiddlewareHandler {

The basic nonce management will be good enough for simple frontends, but it won't work for some gaming use cases that need something like the cached & speculative nonce middleware, so we'll need a new LoomProvider2 that does querying via /eth, but uses the nonce middleware to manage nonces.

[eduardonunesp]

LoomProvider2 will have deeper integration with Web3 now that version 1.2.1 reached a stable cycle and the past issues with the lib are fixed, the next step is to put LoomProvider2 on loom-js, I'm working on that :)