Make CI use a dummy password hasher for all tests (#22983)

During the recent hash algorithm change it became clear that the choice
of password hash algorithm plays a role in the time taken for CI to run.

Therefore as attempt to improve CI we should consider using a dummy
hashing algorithm instead of a real hashing algorithm.

This PR creates a dummy algorithm which is then set as the default
hashing algorithm during tests that use the fixtures. This hopefully
will cause a reduction in the time it takes for CI to run.

---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/auth/password/hash/dummy.go

@@ -0,0 +1,33 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package hash
+
+import (
+	"encoding/hex"
+)
+
+// DummyHasher implements PasswordHasher and is a dummy hasher that simply
+// puts the password in place with its salt
+// This SHOULD NOT be used in production and is provided to make the integration
+// tests faster only
+type DummyHasher struct{}
+
+// HashWithSaltBytes a provided password and salt
+func (hasher *DummyHasher) HashWithSaltBytes(password string, salt []byte) string {
+	if hasher == nil {
+		return ""
+	}
+
+	if len(salt) == 10 {
+		return string(salt) + ":" + password
+	}
+
+	return hex.EncodeToString(salt) + ":" + password
+}
+
+// NewDummyHasher is a factory method to create a DummyHasher
+// Any provided configuration is ignored
+func NewDummyHasher(_ string) *DummyHasher {
+	return &DummyHasher{}
+}