feat: bulletproof SPA recovery

[jordanw66]

Overview

This PR finally delivers the holy trinity of Qwik SPA, specifically:

• Every page arrived at through SPA can be determined by history alone.
• (Nearly) every page can recover the SPA context on popstate after a refresh, navigation away/back, browser session restore, etc. (relies on any Link if present, this can be improved, falls back to reload if not)
• Scroll is saved and restored for every single SPA page, even if the SPA context is lost and not recovered.
• Scroll history is saved directly in history state, impossible to lose, not subject to sessions or storage being lost. Seriously, when the nukes come for us all the last things standing will be twinkie factories, and your scroll states.
• Scroll restore and saving almost perfectly mimics browser native scroll restore. You literally cannot tell the difference, and if you find some small edgecase, it should easily be fixable under this setup.
• This level of SPA recovery doesn't come free, but we "keep it Qwik" by inserting a small shim to replace the old popstate handler. This shim checks if SPA needs to be rebooted, if so it scrolls then manually imports a standalone SPA init QRL to handle the rest. There is essentially 0 impact on MPA pages. The size is comparable to the old handler.
• This standalone SPA init QRL hands off to the useNavigate context once it's restored. It is never sent to users on MPA, instead we pre-cache when the user first upgrades to SPA, this way it's cached and ready for SPA reboots.
• @billykwok's custom restoreScroll$ @alpha api has been removed. It was incompatible with these changes, but I do believe the code in this PR can be extended to provide more customization than any other framework. However, it will take some thought to implement and nail down the correct API. For now, we choose to deliver best-in-class MPA-like scroll experience by default.
• Browsers will natively remember and scroll on every single state. For further resiliency, we patch the history object during an SPA context so that devs who use pushState and replaceState will always maintain scroll history.
• Rewrote and expanded docs on SPA Navigation to be more informative and also added Scroll Restoration docs.
• Fixed a longtime issue where isNavigating should've been set to false after render, instead it was being set before.

With this PR, the SPA experience in Qwik becomes indistinguishable from MPA.

What is it?

• Feature / enhancement
• Bug
• Docs / tests / types / typos

Description

Please include a summary of the change and which issue is fixed. Please also include relevant motivation and context. List any dependencies that are required for this change.

Use cases and why

• 1. One use case
• 2. Another use case

Checklist:

• My code follows the developer guidelines of this project
• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• Added new tests to cover the fix / functionality

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🔨 Latest commit	622618d

[DustinJSilk]

amazing work!

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[jordanw66]

This PR is now pretty much ready, please let me know if this implementation is acceptable. cc @manucorporat

[manucorporat]

At this point the implementation is way over my head, you know more than anybody how this works, but the work seems good and i like the reduced API surface, gonna merge before 1.2 release!

Can u fix the merge conflict?

[shairez]

Wow this is some amazing job @jordanw66 ! 👏👏

(btw, if you are on discord / twitter / myspace, please DM me :)

[jordanw66]

@manucorporat Fixed the merge issue, also rewrote and simplified billy's scroll logic, and discovered a few preexisting bugs in useNavigate and Link and fixed those. I've manually tested the whole SPA pipeline now, seems to work amazing. (should be good for this release)

You can imagine there are probably 100s of edge cases with SPA navigation, I plan to rewrite the whole spa e2e in a future PR to make sure this doesn't get broken and covers all of them. Will take time though, SPA is like a labyrinth and not exactly straightforward.

[manucorporat]

Improving e2e is a must a this point indeed, like @shairez said, if you are discord we can chat about a plan!
Once we have a good structure in place is easy to add new regression tests as issues are reported!

[manucorporat]

Gonna merge!