Java modules: Upgrade to AGP 7.4.0 & Gradle 7.6

Fix the issues that were reported because of that change:

WARNING:The specified Android SDK Build Tools version (28.0.3) is ignored, as it is below the minimum supported version (30.0.3) for Android Gradle Plugin 7.4.0.
Android SDK Build Tools 30.0.3 will be used.
To suppress this warning, remove "buildToolsVersion '28.0.3'" from your build.gradle file, as each version of the Android Gradle Plugin now has a default version of the build tools.

android:exported needs to be explicitly specified for element <activity#com.crocoapps.javafilestoragetest2.MainActivity>. Apps targeting Android 12 and higher are required to specify an explicit value for `android:exported` when the corresponding component has an intent filter defined. See https://developer.android.com/guide/topics/manifest/activity-element#exported for details.

Setting the namespace via a source AndroidManifest.xml's package attribute is deprecated.
Please instead set the namespace (or testNamespace) in the module's build.gradle file, as described here: https://developer.android.com/studio/build/configure-app-module#set-namespace
This migration can be done automatically using the AGP Upgrade Assistant, please refer to https://developer.android.com/studio/build/agp-upgrade-assistant for more information.

.../keepass2android/src/java/KP2ASoftkeyboard_AS/app/src/main/AndroidManifest.xml:5:5-46 Warning:
	uses-sdk:targetSdkVersion value (14) specified in the manifest file is ignored. It is overridden by the value declared in the DSL or the variant API, or 1 if not declared/present. Current value is (18).

src/java/android-filechooser-AS/build.gradle

@@ -9,7 +9,7 @@ buildscript {
         }
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.3.2'
+        classpath "com.android.tools.build:gradle:7.4.0"
 
         // NOTE: Do not place your application dependencies here; they belong
         // in the individual module build.gradle files