Replace Prefire with a very similar but simpler and more direct approach (#3232)

* Replace Prefire with a very similar but simpler and more direct approach

* Move PreviewTest snapshots to their new location (snapshotting default, mirrors UITests)

* Update acknowledgements

* Switch snapshot configuration extensions to a custom version

* Exclude snapshots from the PreviewTests target

* Fix acknowledgements

* Rename snapshotting preference keys

* Remove `skipPackagePluginValidation`

ElementX/Sources/Other/Extensions/Snapshotting.swift

@@ -0,0 +1,58 @@
+//
+// Copyright 2024 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import SwiftUI
+
+public struct SnapshotDelayPreferenceKey: PreferenceKey {
+    public static var defaultValue: TimeInterval = 0.0
+
+    public static func reduce(value: inout TimeInterval, nextValue: () -> TimeInterval) {
+        value = nextValue()
+    }
+}
+
+public struct SnapshotPrecisionPreferenceKey: PreferenceKey {
+    public static var defaultValue: Float = 1.0
+
+    public static func reduce(value: inout Float, nextValue: () -> Float) {
+        value = nextValue()
+    }
+}
+
+public struct SnapshotPerceptualPrecisionPreferenceKey: PreferenceKey {
+    public static var defaultValue: Float = 1.0
+
+    public static func reduce(value: inout Float, nextValue: () -> Float) {
+        value = nextValue()
+    }
+}
+
+public extension SwiftUI.View {
+    /// Use this modifier when you want to apply snapshot-specific preferences,
+    /// like delay and precision, to the view.
+    /// These preferences can then be retrieved and used elsewhere in your view hierarchy.
+    ///
+    /// - Parameters:
+    ///   - delay: The delay time in seconds that you want to set as a preference to the View.
+    ///   - precision: The percentage of pixels that must match.
+    ///   - perceptualPrecision: The percentage a pixel must match the source pixel to be considered a match. 98-99% mimics the precision of the human eye.
+    @inlinable
+    func snapshotPreferences(delay: TimeInterval = .zero, precision: Float = 1.0, perceptualPrecision: Float = 1.0) -> some SwiftUI.View {
+        preference(key: SnapshotDelayPreferenceKey.self, value: delay)
+            .preference(key: SnapshotPrecisionPreferenceKey.self, value: precision)
+            .preference(key: SnapshotPerceptualPrecisionPreferenceKey.self, value: perceptualPrecision)
+    }
+}