DatabaseSource::Auto (#9500)

* implement "auto" database backend in client/db, in progress, #9201

* move fn supports_ref_counting from DatabaseSource enum to Database trait to make it work correctly for all types of dbs

* update kvdb_rocksdb to 0.13 and use it's new config feature  to properly auto start existing database

* tests for auto database reopening

* introduce OpenDbError to cleanup opening database error handling and handle case when database is not enabled at the compile time

* cargo fmt strings again

* cargo fmt strings again

* rename DataSettingsSrc to fix test compilation

* fix the call to the new kvdb-rocksdb interdace in tests to fix compilation

* simplify OpenDbError and make it compile even when paritydb and rocksdb are disabled

* cargo fmt

* fix compilation without flag with-parity-db

* fix unused var compilation warning

* support different paths for rocksdb and paritydb in DatabaseSouce::Auto

* support "auto" database option in substrate cli

* enable Lz4 compression for some of the parity-db colums as per review suggestion

* applied review suggestions

substrate/client/cli/src/arg_enums.rs

@@ -197,6 +197,9 @@ pub enum Database {
 	RocksDb,
 	/// ParityDb. <https://github.com/paritytech/parity-db/>
 	ParityDb,
+	/// Detect whether there is an existing database. Use it, if there is, if not, create new
+	/// instance of paritydb
+	Auto,
 }
 
 impl std::str::FromStr for Database {
@@ -207,6 +210,8 @@ impl std::str::FromStr for Database {
 			Ok(Self::RocksDb)
 		} else if s.eq_ignore_ascii_case("paritydb-experimental") {
 			Ok(Self::ParityDb)
+		} else if s.eq_ignore_ascii_case("auto") {
+			Ok(Self::Auto)
 		} else {
 			Err(format!("Unknown variant `{}`, known variants: {:?}", s, Self::variants()))
 		}
@@ -216,7 +221,7 @@ impl std::str::FromStr for Database {
 impl Database {
 	/// Returns all the variants of this enum to be shown in the cli.
 	pub fn variants() -> &'static [&'static str] {
-		&["rocksdb", "paritydb-experimental"]
+		&["rocksdb", "paritydb-experimental", "auto"]
 	}
 }