Fix NPE in TwaLauncher when fallbackStrategy is null.

There were 2 issues:
* launch(Uri url) uses a null fallbackStrategy. In the
  fallsBackToCustomTab and
  fallsBackToCustomTab_whenSessionCreationFails test cases,
  the custom tab fallbackStrategy is supposed to be used, but
  it's null.
* The TestCustomTabsService is supposed to support the
  CustomTabsService action.

Author: ericsum26

androidbrowserhelper/src/androidTest/AndroidManifest.xml

@@ -57,7 +57,7 @@
         <service android:name="com.google.androidbrowserhelper.trusted.testcomponents.TestCustomTabsService"
                  android:enabled="false" android:exported="true">
             <intent-filter>
-                <category android:name="androidx.browser.trusted.category.TrustedWebActivities" />
+                <action android:name="android.support.customtabs.action.CustomTabsService" />
             </intent-filter>
         </service>
 

androidbrowserhelper/src/androidTest/java/com/google/androidbrowserhelper/trusted/TwaLauncherTest.java

@@ -132,7 +132,8 @@ public void fallsBackToCustomTab() {
         mEnableComponents.manuallyDisable(TestCustomTabsServiceSupportsTwas.class);
         TwaLauncher launcher = new TwaLauncher(mActivity);
 
-        Runnable launchRunnable = () -> launcher.launch(URL);
+        Runnable launchRunnable = () -> launcher.launch(new TrustedWebActivityIntentBuilder(URL),
+                mCustomTabsCallback, null, null, TwaLauncher.CCT_FALLBACK_STRATEGY);
         Intent intent = getBrowserActivityWhenLaunched(launchRunnable).getIntent();
 
         launcher.destroy();
@@ -143,7 +144,8 @@ public void fallsBackToCustomTab() {
     public void fallsBackToCustomTab_whenSessionCreationFails() {
         TestCustomTabsService.setCanCreateSessions(false);
 
-        Runnable launchRunnable = () -> mTwaLauncher.launch(URL);
+        Runnable launchRunnable = () -> mTwaLauncher.launch(new TrustedWebActivityIntentBuilder(URL),
+                mCustomTabsCallback, null, null, TwaLauncher.CCT_FALLBACK_STRATEGY);
         TestBrowser browser = getBrowserActivityWhenLaunched(launchRunnable);
         assertFalse(browser.getIntent().getBooleanExtra(EXTRA_LAUNCH_AS_TRUSTED_WEB_ACTIVITY,
                 false));