Bit: use exec-out instead of shell

By switching to 'adb exec-out' instead of 'adb shell', characters such
as # no longer need to be escaped when executing a single
instrumentation method. The new syntax is simply

  $ bit module:class#method

Note: the old syntax (module:class\#method) still works.

Test: manual: bit InternalTests:android.app.WallpaperColorsTest#colorHintsTest, test should execute
Change-Id: I8c86faf2ccaf84834030f6ba7567cb4cecd37bc6