Improves grouped condition trait preparation swiftlang#1034

Updates the `GroupedConditionTrait` to prepare for tests concurrently, improving performance.

Also adds a check to ensure there are at least two condition traits before attempting to operate on them, preventing potential errors.

Author: hrayatnia

Sources/Testing/Traits/ConditionTrait.swift

@@ -239,11 +239,23 @@ public struct GroupedConditionTrait: TestTrait, SuiteTrait {
   var operations: [Operation] = []
 
   public func prepare(for test: Test) async throws {
-    for (index, operation) in operations.enumerated() {
-      try await operation.operate(conditionTraits[index], conditionTraits[index + 1], includeSkipInfo: true)
-    }
+      let traitCount = conditionTraits.count
+      guard traitCount >= 2 else { return }
+      
+      try await withThrowingTaskGroup(of: Void.self) { group in
+          for (index, operation) in operations.enumerated() where index < traitCount - 1 {
+              let trait1 = conditionTraits[index]
+              let trait2 = conditionTraits[index + 1]
+              group.addTask {
+                  try await operation.operate(trait1, trait2, includeSkipInfo: true)
+              }
+          }
+
+          try await group.waitForAll()
+      }
   }
 
+  @_spi(Experimental)
   public func evaluate() async throws -> Bool {
       var result: Bool = true
       for (index, operation) in operations.enumerated() {