feat: Add Screenshots automatically.

[lucas-zimerman]

This WIP feature allows adding screenshots to events whenever possible.

new Sentry options:

• AttachScreenshots: Attaches screenshots from the app to events automatically whenever possible.
• ScreenshotQuality: (Low, Medium, High) allows the user to choose the quality of the screenshots (default low for lower file sizes)
• file format: Jpeg whenever available.

Goals

* Use of native code so that porting this feature becomes easier to native SDKs.

• Support iOS, Android, and UWP (other platforms doesn't support attaching a screenshot exclusively from the application)
• Have an event processor that can inject attachments to an event being processed.

Sample Event: https://sentry.io/organizations/sentry-sdks/discover/sentry-xamarin:970c172209f54cf3827b0f3813185764

I suggest the usage of jpeg by default due to the lower performance impact compared to png encoding (see: https://blender.stackexchange.com/questions/148231/what-image-format-encodes-the-fastest-or-at-least-faster-png-is-too-slow)

Challenges

• Event Processors doesn't allow the insertion of attachments directly into events, requiring you to edit the scope (and with that, the screenshot may be attached to all future events and not the current one)

[ueman]

This should probably include a note about PII.
There could be potentially private information in the screenshot. For example in bank or chat apps.

[lucas-zimerman]

I agree

[bruno-garcia]

We should release a preview with this

[bruno-garcia]

@lucas-zimerman no changelog entry?

No Danger? :)