QScreenCapture fails silently when Service not in manifest

When using QScreenCapture on Android, it is a requirement that we include specific Services and permissions in order to successfully perform a screen-capturing session.
However, if the application developer fails to follow through with this step, they get no indication from our public APIs that this operation failed.

Here is what currently happens:

1. Run QScreenCapture::start()
2. onActiveChanged is called, the new value is true. (Even though no frames are emitted)
3. UI thread freezes while the content picker is shown
4. Sometimes we will get a log output mentioning a Java exception. This was hard to reproduce consistently.
5. The 'active' property will be left set to true, no error signal will have been raised and no frames are emitted.

What I expect to happen:

1. Run QScreenCapture::start()
2. onActiveChanged is not emitted. Active is not set to true. Attempts to run `start()` while the content-picker is active is ignored.
3. Content picker is NOT shown. (We should detect missing manifest ahead of time)
4. Error signal is raised with appropriate error message.
5. Active property is stays false.

This was observed on the following devices:

• Samsung Galaxy Tab A8, running Android 14
• Motorola Razr 40 Ultra, running Android 15