Add SensitiveUrl to redact user secrets from endpoints (#2326)

## Issue Addressed

#2276 

## Proposed Changes

Add the `SensitiveUrl` struct which wraps `Url` and implements custom `Display` and `Debug` traits to redact user secrets from being logged in eth1 endpoints, beacon node endpoints and metrics.

## Additional Info

This also includes a small rewrite of the eth1 crate to make requests using `Url` instead of `&str`. 
Some error messages have also been changed to remove `Url` data.

beacon_node/http_api/Cargo.toml

@@ -35,3 +35,4 @@ store = { path = "../store" }
 environment = { path = "../../lighthouse/environment" }
 tree_hash = "0.1.1"
 discv5 = { git = "https://github.com/sigp/discv5 ", rev = "02d2c896c66f8dc2b848c3996fedcd98e1dfec69", features = ["libp2p"] }
+sensitive_url = { path = "../../common/sensitive_url" }