[benchmark] Add .existential BenchmarkCategory

Author: palimondo

benchmark/single-source/ExistentialPerformance.swift

@@ -18,8 +18,8 @@
 
 import TestsUtils
 
-let t: [BenchmarkCategory] = []
-let ta: [BenchmarkCategory] = [.api, .Array]
+let t: [BenchmarkCategory] = [.existential]
+let ta: [BenchmarkCategory] = [.api, .Array, .existential]
 
 public let ExistentialPerformance: [BenchmarkInfo] = [
   BenchmarkInfo(name: "Existential.method.1x.Ref1",

benchmark/single-source/ExistentialPerformance.swift.gyb

@@ -19,8 +19,8 @@
 
 import TestsUtils
 
-let t: [BenchmarkCategory] = []
-let ta: [BenchmarkCategory] = [.api, .Array]
+let t: [BenchmarkCategory] = [.existential]
+let ta: [BenchmarkCategory] = [.api, .Array, .existential]
 
 %{
 Setup = """

benchmark/utils/TestsUtils.swift

@@ -25,7 +25,7 @@ public enum BenchmarkCategory : String {
   case sdk
   case runtime, refcount, metadata
   // Other general areas of compiled code validation.
-  case abstraction, safetychecks, exceptions, bridging, concurrency
+  case abstraction, safetychecks, exceptions, bridging, concurrency, existential
 
   // Algorithms are "micro" that test some well-known algorithm in isolation:
   // sorting, searching, hashing, fibonaci, crypto, etc.