dashboard: fix subprocesses blocking the event loop (#5772)

* dashboard: fix subprocesses blocking the event loop

- break apart the util module
- adds a new util to run subprocesses with asyncio

* take a list

esphome/dashboard/util/password.py

@@ -0,0 +1,11 @@
+from __future__ import annotations
+
+import hashlib
+
+
+def password_hash(password: str) -> bytes:
+    """Create a hash of a password to transform it to a fixed-length digest.
+
+    Note this is not meant for secure storage, but for securely comparing passwords.
+    """
+    return hashlib.sha256(password.encode()).digest()