Add visionOS unit tests, unit test targets, test app, testing host app, and xcconfigs

[mipetriu]

Proposed changes

This PR adds a visionOS test app in MSAL mostly taken from the publicly available iOS Graph API sample. Keeping these files separate should allow for more simple review of the overall visionOS changes needed in MSAL: #1990

Type of change

• Feature work
• Bug fix
• Documentation
• Engineering change
• Test
• Logging/Telemetry

Risk

• High – Errors could cause MAJOR regression of many scenarios. (Example: new large features or high level infrastructure changes)
• Medium – Errors could cause regression of 1 or more scenarios. (Example: somewhat complex bug fixes, small new features)
• Small – No issues are expected. (Example: Very small bug fixes, string changes, or configuration settings changes)

Additional information

[azure-pipelines]

This pull request does not update CHANGELOG.md.

Please consider if this change would be noticeable to a partner or user and either update CHANGELOG.md or resolve this conversation.

[frogcjn]

I have improved the xcconfig parts for visionOS and building XCFramework process which developer could build themselves swift package version of MSAL, you could check the pull request at #2065

[tkukielk]

I don't think you need to add any architectures to ARCHS_STANDARD for iOS or visionOS

[tkukielk]

bitcode is long deprecated for iOS and is not available for visionOS

[tkukielk]

Per our conversation it would be much easier just to add the following to the global/shared xcconfig and not create a separate target for visionOS:

SUPPORTED_PLATFORMS = iphoneos iphonesimulator xros xrsimulator
// 1: iPhone, 2: iPad, 3: appleTV, 7: vision
// when left empty, uses one default device for given platform
TARGETED_DEVICE_FAMILY[sdk=iphone*] = 1,2

The differences between iOS and visionOS in your code are minor and can easily be handled with compile time #ifs in the sources. This will simplify usage of your library in clients building for different iOS-derived platforms.