[Code health] Clean up flow of state in SubmissionService

[gino-m]

• Remove select and deselect methods and submissionId state; change submission id via NavigationService instead.
• Use combineLatestAll to combine at active survey, selected LOI, current user and submissionId$ in NavigationService. Use distinctUntilChanged on the result of combineLatestAll to avoid hitting db multiple times.
• Emit LOADING when any of the above changes, then loadSubmission$ - use distinctUntilChanged on return value of stream.
• Remove unused code from MainPageComponent

@rfontanarosa

EDIT: From standup today Oct 23 2024, this above proposal is no longer feasible and needs to be discussed

[jcqli]

Related to Async issues with RxJs

[gino-m]

Trying to make Beta scope tractable; let's tackle this as part of the push for GA.

[gino-m]

@rfontanarosa Can you meet Daniel to discuss splitting this into smaller tasks?