* add eth_depositById rpc method

* add sample depositById test

* change ethereum to bor

* add subscription for new deposit data

* create channel to listen new state change

* push state data to subcribed channel

* apply filter on deposit events sub

* remove unused methods

* Fix: no filter

* Remove unused method

* revert changes

* Fix: RPC port

* refactor and cleanup

* Fix: SubscribeStateEvent

* remove unused import

* Resolve comments

Co-authored-by: Arpit Agarwal <93arpit@gmail.com>

* Fix typo in interfaces.go

* Update interfaces.go

Fix a spelling mistake in comment

There is no need to depend on the old context package now that the
minimum Go version is 1.7. The move to "context" eliminates our weird
vendoring setup. Some vendored code still uses golang.org/x/net/context
and it is now vendored in the normal way.

This change triggered new vet checks around context.WithTimeout which
didn't fire with golang.org/x/net/context.

This significantly reduces the dependency closure of ethclient, which no
longer depends on core/vm as of this change.

All uses of vm.Logs are replaced by []*types.Log. NewLog is gone too,
the constructor simply returned a literal.

ethclient now returns ethereum.NotFound if the server returns null and
no error while accessing blockchain data.

The light client cannot provide arbitrary transactions. The change to
split transaction access into its own interface emphasizes that
transactions should not be relied on and recommends use of logs.