Add tests for GL_EXT_debug_marker

This adds simple support check, randomized, and invalid usage tests for
GL_EXT_debug_marker to the ES2 test module.

Android framework requires GL_EXT_debug_marker extension so tests will
fail on Android unless the extension is supported. On other platforms
the usual convention of reporting NotSupported is followed.

Bug: 21333653
Bug: 18315793
Change-Id: Id73c64e091533564698c736fcdbe24e216481354
18 files changed