android: Update compileSdkVersion/targetSdkVersion to 31

Google Play now requires that apps target API level 30 or higher, and
compileSdkVersion/targetSdkVersion 31 is also needed to update
the com.google.android.material dependency to >= 1.5.0 [1].

Explicitly set the `android:exported="true"` attribute for activities
which is required when targeting Android 12 or newer; quoting from
the list of behavior changes for apps targeting Android 12 [1]:

> Safer component exporting
>
> If your app targets Android 12 or higher and contains activities,
> services, or broadcast receivers that use intent filters, you must
> explicitly declare the android:exported attribute for these app
> components.  Warning: If an activity, service, or broadcast receiver
> uses intent filters and doesn't have an explicitly-declared value for
> android:exported, your app can't be installed on a device that runs
> Android 12 or higher.
>
> If the app component includes the LAUNCHER category, set
> android:exported to true. In most other cases, set android:exported
> to false.
>
> The following code snippet shows an example of a service that
> contains an intent filter whose android:exported attribute is set to
> false:
>
> <service android:name="com.example.app.backgroundService"
>          android:exported="false">
>     <intent-filter>
>         <action android:name="com.example.app.START_BACKGROUND" />
>     </intent-filter>
> </service>

The app worked fine in a quick test on an x86_64 AVD with API level 31.

[1] https://github.com/material-components/material-components-android/releases/tag/1.5.0-alpha03

Change-Id: Ibb919e4edb995740e48ebc3338ffab6ca35c1373
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/133167
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

0 files changed, 0 insertions, 0 deletions