Remove rc-1 preview tag for v7.0

Adjust to rc-1

Warn when packages.config in use (#2329)

Also fixed incorrect System.Threading.Tasks.Extensions version in nuspec, which was causing a load of warnings when used with an old-style .NET FX project.

Use VS2022-compatible Roslyn refs in analyzers (#2319)

We had been using V5. This is unavailable on VS2022 - it's VS2026 only. We've now downgraded the reference to 4.12, because that's the version available on the oldest LTS version of VS2022 still in support (17.12 - still in support until 15th July 2026).

Add UWP package and tidy the analyzers (#2316)

* Analyzer tests now simulate UWP builds
* Extension method analyzers now table-driven, significantly simplifying logic, and making it much easier to see what cases we handle
* Update packaging ADR
* Add System.Reactive.Uwp and update analyzers
* Analyzer IAsyncAction/Operation support
* Detect ToEventPattern extension method
* Detect WindowsObservable and IEventPatternSource`2
* Remove workaround for Microsoft.CodeAnalysis.Analyzer.Testing 1.1.2 bug
* Link to ADR 0005 in readmes and release notes.

Fix version

Release prep for Ix v7.0.1 (#2313)

Set version to '7.0.0'

Generate AsyncEnumerableDeprecated facade in runtime assembly (#2293)

Remove AsyncEnumerable from System.Linq.Async public API (#2292)