refactor: initiating install process
Description
The source code of initiating of app install process was spread out in different layers. Now those source codes are centralized in a single class.
Technical details
Initiating app install process related codes (creating FusedDownload and inserting into DB, checking corner cases) were implemented in MainActivity, MainActivityViewModel, UpdatedWorker. There were some duplicate codes as well. Now All these things are moved to AppInstallProcessor.
Updated the method calculateAvailableDiskSpace(), Updated one calculate the space is available in data directory to calculate the available space to install an app more accurately. before this method was used.