DB transactions now follow the resource control ResourceAcquire and ResourceRelease types

* Provided `iterator` methods to `DB` and `DBTransaction` to enable transactional iterators
* Remove `DB.withLocks` and `DB.transact` as advisory locking is now the responsibility of the user
* Root sublevels have been created `data` and `transactions`
* Transactions have isolation level and read-phenomena tests
* New methods on DB: `iterator`, `clear`, `count`, `dump`
* New methods on DBTransaction: `iterator`, `clear`, `count`, `dump`

Author: CMCDragonkai

package.json

@@ -24,7 +24,6 @@
     "@matrixai/logger": "^2.1.0",
     "@matrixai/workers": "^1.2.5",
     "abstract-leveldown": "^7.2.0",
-    "async-mutex": "^0.3.1",
     "level": "7.0.1",
     "levelup": "^5.1.1",
     "sublevel-prefixer": "^1.0.0",

shell.nix

@@ -13,6 +13,9 @@ pkgs.mkShell {
     set +o allexport
     set -v
 
+    # Enables npm link to work
+    export npm_config_prefix=~/.npm
+
     export PATH="$(pwd)/dist/bin:$(npm bin):$PATH"
     npm install
     mkdir --parents "$(pwd)/tmp"