Remove go_router dependency for navigation

[hjiangsu]

Pull Request Description

This PR removes our dependency on go_router, and migrates our existing usage of go_router with the built in Navigator. There's a few reasons for this refactor:

• We currently use a mix of go_router and Navigator. Since we are only using go_router for the Settings page, it seems a bit redundant to have the package when we could implement the same logic using Navigator. Thus, it makes more sense to use Navigator unless we require a specific feature from go_router (e.g., ShellRoutes)
• Using only one of Navigator / go_router allows us to simplify state restoration later on (e.g., when the app is killed by the OS to free up memory). Navigator has a simple method of creating restorable states whereas go_router is a bit more complex (and may not fully work well in some cases)

This is still in draft as there's a bit more testing / refining that is needed:

• Testing deep links on Android / iOS (tapping a link from outside Thunder to open in Thunder)
• DONE: Testing of routing within the Settings page to ensure all routing is properly handled (also, checking to see if Thunder-setting links open up properly Add ability to create links to settings. #1348)

Issue Being Fixed

This tangentially relates to, and is a first step to hopefully solving #1607. There is still a lot of additional steps that is required, but being able to restore the navigation state is the first step (e.g., to be able to navigate back to the CreatePostPage)

Issue Number: N/A

Screenshots / Recordings

Checklist

• If a new package was added, did you ensure it uses an appropriate license and is actively maintained?
• Did you use localized strings (and added appropriate descriptions) where applicable?
• Did you add semanticLabels where applicable for accessibility?

[hjiangsu]

Update: I found the issue and applied the fix here since it seems fairly small - this is the commit which fixes the issue (at least on iOS): 1f7e2ba

Original comment:
So after some testing, it turns out that deep links does not seem to work in the current build on iOS (both develop and this branch).

@micahmo Could you check if deep linking works on the current develop for Android? If it's not working on Android either, I'll open up a new PR for that issue rather than to place the fix here.

Aside from that, I've tested everything else and it should be working so this is ready to go!

[micahmo]

The code LGTM! Did you still need me to test anything in particular?

[micahmo]

@micahmo Could you check if deep linking works on the current develop for Android?

Yes deep links are still working fine in develop!