Move various Shell tests into a subdir.

TBR=sky@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1706833003

Cr-Commit-Position: refs/heads/master@{#376255}

• BUILD.gn[diff]
• mojo/BUILD.gn[diff]
• mojo/mojo_shell.gyp[diff]
• mojo/shell/BUILD.gn[diff]
• mojo/shell/tests/BUILD.gn[Added - diff]
• mojo/shell/tests/application_manager_apptest.cc[Renamed from mojo/shell/application_manager_apptest.cc - diff]
• mojo/shell/tests/application_manager_apptest_driver.cc[Renamed from mojo/shell/application_manager_apptest_driver.cc - diff]
• mojo/shell/tests/application_manager_apptest_driver_manifest.json[Renamed from mojo/shell/application_manager_apptest_driver_manifest.json - diff]
• mojo/shell/tests/application_manager_apptest_manifest.json[Renamed from mojo/shell/application_manager_apptest_manifest.json - diff]
• mojo/shell/tests/application_manager_apptest_target.cc[Renamed from mojo/shell/application_manager_apptest_target.cc - diff]
• mojo/shell/tests/application_manager_apptests.mojom[Renamed from mojo/shell/application_manager_apptests.mojom - diff]
• mojo/shell/tests/application_manager_unittest.cc[Renamed from mojo/shell/application_manager_unittest.cc - diff]
• mojo/shell/tests/capability_filter_test.cc[Renamed from mojo/shell/capability_filter_test.cc - diff]
• mojo/shell/tests/capability_filter_test.h[Renamed from mojo/shell/capability_filter_test.h - diff]
• mojo/shell/tests/capability_filter_unittest.cc[Renamed from mojo/shell/capability_filter_unittest.cc - diff]
• mojo/shell/tests/capability_filter_unittest.mojom[Renamed from mojo/shell/capability_filter_unittest.mojom - diff]
• mojo/shell/tests/package_apptest.cc[Renamed from mojo/shell/package_apptest.cc - diff]
• mojo/shell/tests/package_test.mojom[Renamed from mojo/shell/package_test.mojom - diff]
• mojo/shell/tests/package_test_app_a_manifest.json[Renamed from mojo/shell/package_test_app_a_manifest.json - diff]
• mojo/shell/tests/package_test_app_b_manifest.json[Renamed from mojo/shell/package_test_app_b_manifest.json - diff]
• mojo/shell/tests/package_test_package.cc[Renamed from mojo/shell/package_test_package.cc - diff]
• mojo/shell/tests/package_test_package_manifest.json[Renamed from mojo/shell/package_test_package_manifest.json - diff]
• mojo/shell/tests/test.mojom[Renamed from mojo/shell/test.mojom - diff]