Add MauiUIApplicationDelegate.PerformFetch

[jfversluis]

Description of Change

Seems like we didn't add the MauiUIApplicationDelegate.PerformFetch as a virtual to override.

Issues Fixed

Fixes #7957

[jfversluis]

@mattleibow not sure if you're the right person but saw some recent changes from you here. Is this the right way to go about this? And I guess this should target the net7 branch?

[mattleibow]

Main is correct as it is pseudo net7.

But for this, could we also add delegates for the life cycle events? This way, users do not have to override in order to hook in to it.

[jsuarezruiz]

/azp run

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Azure Pipelines successfully started running 2 pipeline(s).

[edgiardina]

Just voting for the LifeCycleEvents approach.

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[jfversluis]

@mattleibow it's been a while! But finally got to update this one, so it you please...

[edgiardina]

Love that the delegates are there. I ended up implementing Shiny.NET Jobs in their prerelease MAUI packages as a workaround, which offered a crossplatform way to implement backgrounding.
https://shinylib.net/mobile/jobs/index.html?tabs=ios

But exposing the iOS via the delegates is awesome too. Thank you.