Add test for new-bench

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/Bar.hs

+main = putStrLn "Hello Bar"

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/Foo.hs

+main = putStrLn "Hello Foo"

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/MultipleBenchmarks.cabal

+name: MultipleBenchmarks
+version: 1.0
+build-type: Simple
+cabal-version: >= 1.10
+
+benchmark foo
+    type: exitcode-stdio-1.0
+    main-is: Foo.hs
+    build-depends: base
+    default-language: Haskell2010
+
+benchmark bar
+    type: exitcode-stdio-1.0
+    main-is: Bar.hs
+    build-depends: base
+    default-language: Haskell2010
+

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/cabal.out

+# cabal new-bench
+Resolving dependencies...
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - MultipleBenchmarks-1.0 (bench:foo) (first run)
+Configuring benchmark 'foo' for MultipleBenchmarks-1.0..
+Preprocessing benchmark 'foo' for MultipleBenchmarks-1.0..
+Building benchmark 'foo' for MultipleBenchmarks-1.0..
+Running 1 benchmarks...
+Benchmark foo: RUNNING...
+Benchmark foo: FINISH
+# cabal new-bench
+Build profile: -w ghc-<GHCVER> -O1
+In order, the following will be built:
+ - MultipleBenchmarks-1.0 (bench:bar) (first run)
+ - MultipleBenchmarks-1.0 (bench:foo) (first run)
+Configuring benchmark 'bar' for MultipleBenchmarks-1.0..
+Preprocessing benchmark 'bar' for MultipleBenchmarks-1.0..
+Building benchmark 'bar' for MultipleBenchmarks-1.0..
+Running 1 benchmarks...
+Benchmark bar: RUNNING...
+Benchmark bar: FINISH
+Preprocessing benchmark 'foo' for MultipleBenchmarks-1.0..
+Building benchmark 'foo' for MultipleBenchmarks-1.0..
+Running 1 benchmarks...
+Benchmark foo: RUNNING...
+Benchmark foo: FINISH

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/cabal.project

+packages: .

cabal-testsuite/PackageTests/NewBuild/CmdBench/MultipleBenchmarks/cabal.test.hs

+import Test.Cabal.Prelude
+
+main = cabalTest $ do
+    res1 <- cabal' "new-bench" ["foo"]
+    assertOutputContains "Hello Foo" res1
+    assertOutputDoesNotContain "Hello Bar" res1
+    res2 <- cabal' "new-bench" ["all"]
+    assertOutputContains "Hello Foo" res2
+    assertOutputContains "Hello Bar" res2
+