Build universal iOS framework

[AArnott]

Most importantly, this exposes the native library as a "framework" in iOS so that a consuming iOS application will not be rejected by the App Store.

In addition to this though, we combine both x64 and arm64 simulator binaries into one universal binary, which should help make things "just work" whether the simulator runs on an x64 or an arm64 (Apple Silicone) mac.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 20.82%. Comparing base (a143ecf) to head (95bff41).
Report is 5 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #54   +/-   ##
=======================================
  Coverage   20.82%   20.82%           
=======================================
  Files          10       10           
  Lines         317      317           
  Branches       50       50           
=======================================
  Hits           66       66           
  Misses        245      245           
  Partials        6        6           

Flag	Coverage Δ
LinuxHost	20.82% <ø> (ø)
Release	20.82% <ø> (ø)
WindowsHost	20.82% <ø> (ø)
macOSHost	20.82% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[AArnott]

This change mostly looks good. But we have one issue and one question:

Issue

https://github.com/AArnott/iOSSampleInteropApp is a minimum iOS app to test this change. It builds at runtime, and appears to copy the native as well as the managed libraries into the app when targeting the emulator. But the app crashes with a DllNotFoundException when the native library is requires, saying that nerdbank_qrcodes couldn't be found. Why?

**System.DllNotFoundException:** 'nerdbank_qrcodes'

Since the file layout is equivalent to that used by the Sentry.Bindings.Cocoa package (which presumably works), I suspect the problem is in how I prepare the binary files.
The azure-pipelines/build_ios_framework.ps1 file introduce this PR makes use of lipo, install_name_tool and chmod based on what I could gather from a bunch of StackOverflow pages and other projects I could find on GitHub. But I don't fully understand how it's meant to work so I may have made a mistake there.

Open question

Is laying out the nupkg such that the native Apple framework is under the lib/net8.0-ios directory in a special resource pack the best way to go? It's the only way I can find that leads to MSBuild's Xamarin.iOS SDK automatically finding and deploying the right files. The alternative was to place it under the runtimes/ios-universal folder and add a buildTransitive/ import that adds a NativeReference item to the consuming project.

The package layout as it stands now

D:\PACKAGES\NUGET\NERDBANK.QRCODES\0.2.55-BETA-G209A879921
|   .nupkg.metadata
|   nerdbank.qrcodes.0.2.55-beta-g209a879921.nupkg
|   nerdbank.qrcodes.0.2.55-beta-g209a879921.nupkg.sha512
|   nerdbank.qrcodes.nuspec
|   README.md
|   THIRD_PARTY_DEPENDENCIES.txt
|   THIRD_PARTY_LICENSES.yml
|   
+---lib
|   +---net8.0
|   |       Nerdbank.QRCodes.dll
|   |       Nerdbank.QRCodes.xml
|   |       
|   +---net8.0-ios17.5
|   |   |   Nerdbank.QRCodes.dll
|   |   |   Nerdbank.QRCodes.xml
|   |   |   
|   |   \---Nerdbank.QRCodes.resources
|   |       |   manifest
|   |       |   
|   |       \---nerdbank_qrcodes.xcframework
|   |           |   Info.plist
|   |           |   
|   |           +---ios-arm64
|   |           |   \---nerdbank_qrcodes.framework
|   |           |           Info.plist
|   |           |           nerdbank_qrcodes
|   |           |           
|   |           \---ios-arm64_x86_64-simulator
|   |               \---nerdbank_qrcodes.framework
|   |                       Info.plist
|   |                       nerdbank_qrcodes
|   |                       
|   \---net8.0-windows7.0
|           Nerdbank.QRCodes.dll
|           Nerdbank.QRCodes.xml
|           
\---runtimes
    +---android-arm64
    |   \---native
    |           libnerdbank_qrcodes.so
    |           
    +---android-x64
    |   \---native
    |           libnerdbank_qrcodes.so
    |           
    +---linux-arm64
    |   \---native
    |           libnerdbank_qrcodes.so
    |           
    +---linux-x64
    |   \---native
    |           libnerdbank_qrcodes.so
    |           
    +---osx-arm64
    |   \---native
    |           libnerdbank_qrcodes.dylib
    |           
    +---osx-x64
    |   \---native
    |           libnerdbank_qrcodes.dylib
    |           
    +---win-arm64
    |   \---native
    |           nerdbank_qrcodes.dll
    |           
    \---win-x64
        \---native
                nerdbank_qrcodes.dll

[AArnott]

Possibly relevant tip: xamarin/xamarin-macios#21238