Expand remote keystore interface to allow for hybrid mode (#7628)

* update to latest master

* updates on docs, license, meta

* hide ssrs behind feature flag

* implement remaining functions on the server

* sign server line length fix

* fix tests

* fixup in-memory-keystore

* adding failsafe

* skipping ecdsa test for now

* remote keystore param

* remote sign urls made available

* integrating keystore remotes features

* don't forget the dependency

* remove old cruft

* reset local keystore

* applying suggestions

* Switch to single remote, minor grumbles

* minor grumbles, docs

substrate/utils/browser/src/lib.rs

@@ -75,6 +75,7 @@ where
 
 			DatabaseConfig::Custom(sp_database::as_database(db))
 		},
+		keystore_remote: Default::default(),
 		keystore: KeystoreConfig::InMemory,
 		default_heap_pages: Default::default(),
 		dev_key_seed: Default::default(),