[Foundation] Unify a few NSAttributedString functions.

[rolfbjarne]

Unify the code for the following functions:

• NSAttributedString.GetData[FromRange]
• NSAttributedString.GetFileWrapper[FromRange]

These functions use 'ref' arguments instead of 'out' arguments for mobile
platforms (likely due to the generator not having proper 'out' parameter
support when these functions were implemented), so improve to use 'out'
parameters in XAMCORE_5_0 (and macOS, where they already use 'out'
parameters).

Also fix nullability.

Ref: #15216

[vs-mobiletools-engineering-service2]

📚 [PR Build] Artifacts 📚

Artifacts were not provided.

Pipeline on Agent XAMMINI-011.Monterey'
Hash: 8d7459d2bea2db2496f686c1ac620cca534b0b52 [PR build]

[vs-mobiletools-engineering-service2]

✅ API diff for current PR / commit

Legacy Xamarin (No breaking changes)

• iOS: vsdrops gist (No breaking changes)
• tvOS: vsdrops gist (No breaking changes)
• watchOS: vsdrops gist (No breaking changes)
• macOS (no change detected)

.NET (No breaking changes)

• iOS: vsdrops gist (No breaking changes)
• tvOS: vsdrops gist (No breaking changes)
• MacCatalyst: vsdrops gist (No breaking changes)
• macOS: (empty diff detected)

❗ API diff vs stable (Breaking changes)

Legacy Xamarin (:heavy_exclamation_mark: Breaking changes :heavy_exclamation_mark:)

• iOS: vsdrops gist (:heavy_exclamation_mark: Breaking changes :heavy_exclamation_mark:)
• tvOS: vsdrops gist (No breaking changes)
• watchOS: vsdrops gist (No breaking changes)
• macOS: vsdrops gist (No breaking changes)

.NET (:heavy_exclamation_mark: Breaking changes :heavy_exclamation_mark:)

• iOS: vsdrops gist (:heavy_exclamation_mark: Breaking changes :heavy_exclamation_mark:)
• tvOS: vsdrops gist (No breaking changes)
• MacCatalyst: vsdrops gist (No breaking changes)
• macOS: vsdrops gist (No breaking changes)
• Microsoft.iOS vs Microsoft.MacCatalyst: vsdrops gist

Legacy Xamarin (stable) vs .NET

• iOS: vsdrops gist
• tvOS: vsdrops gist
• macOS: vsdrops gist

ℹ️ Generator diff

Generator Diff: vsdrops (html) vsdrops (raw diff) gist (raw diff) - Please review changes)

Pipeline on Agent
Hash: 8d7459d2bea2db2496f686c1ac620cca534b0b52 [PR build]

[vs-mobiletools-engineering-service2]

❌ [PR Build] Tests on macOS M1 - Mac Big Sur (11.5) failed ❌

Failed tests are:

• xammac_tests
• monotouch-test

Pipeline on Agent
Hash: 8d7459d2bea2db2496f686c1ac620cca534b0b52 [PR build]

[vs-mobiletools-engineering-service2]

🚀 [CI Build] Test results 🚀

Test results

✅ All tests passed on VSTS: simulator tests.

🎉 All 223 tests passed 🎉

Tests counts

✅ bcl: All 69 tests passed. Html Report (VSDrops) Download
✅ cecil: All 1 tests passed. Html Report (VSDrops) Download
✅ dotnettests: All 1 tests passed. Html Report (VSDrops) Download
✅ fsharp: All 7 tests passed. Html Report (VSDrops) Download
✅ framework: All 8 tests passed. Html Report (VSDrops) Download
✅ generator: All 2 tests passed. Html Report (VSDrops) Download
✅ interdependent_binding_projects: All 7 tests passed. Html Report (VSDrops) Download
✅ install_source: All 1 tests passed. Html Report (VSDrops) Download
✅ introspection: All 8 tests passed. Html Report (VSDrops) Download
✅ linker: All 65 tests passed. Html Report (VSDrops) Download
✅ mac_binding_project: All 1 tests passed. Html Report (VSDrops) Download
✅ mmp: All 2 tests passed. Html Report (VSDrops) Download
✅ mononative: All 12 tests passed. Html Report (VSDrops) Download
✅ monotouch: All 23 tests passed. Html Report (VSDrops) Download
✅ msbuild: All 2 tests passed. Html Report (VSDrops) Download
✅ mtouch: All 1 tests passed. Html Report (VSDrops) Download
✅ xammac: All 3 tests passed. Html Report (VSDrops) Download
✅ xcframework: All 8 tests passed. Html Report (VSDrops) Download
✅ xtro: All 2 tests passed. Html Report (VSDrops) Download

Pipeline on Agent
Hash: $(GIT_HASH) [PR build]