Make default hash lib configurable without code changes via CLI argument (#3947)

* cli_args: Add --duplicate-check-hash-function.

* server.py: compare_image_hash configurable hash function

Uses an argument added in cli_args to specify the type of hashing to default to for duplicate hash checking.  Uses an `eval()` to identify the specific hashlib class to utilize, but ultimately safely operates because we have specific options and only those options/choices in the arg parser.  So we don't have any unsafe input there.

* Add hasher() to node_helpers

* hashlib selection moved to node_helpers

* default-hashing-function instead of dupe checking hasher

This makes a default-hashing-function option instead of previous selected option.

* Use args.default_hashing_function

* Use safer handling for node_helpers.hasher()

Uses a safer handling method than `eval` to evaluate default hashing function.

* Stray parentheses are evil.

* Indentation fix.

Somehow when I hit save I didn't notice I missed a space to make indentation work proper.  Oops!

node_helpers.py

@@ -1,3 +1,7 @@
+import hashlib
+
+from comfy.cli_args import args
+
 from PIL import ImageFile, UnidentifiedImageError
 
 def conditioning_set_values(conditioning, values={}):
@@ -22,3 +26,12 @@ def pillow(fn, arg):
         if prev_value is not None:
             ImageFile.LOAD_TRUNCATED_IMAGES = prev_value
         return x
+
+def hasher():
+    hashfuncs = {
+        "md5": hashlib.md5,
+        "sha1": hashlib.sha1,
+        "sha256": hashlib.sha256,
+        "sha512": hashlib.sha512
+    }
+    return hashfuncs[args.default_hashing_function]