Support typed rows for C# 13 params ReadOnlySpan<T> parameters #7462

Summary

Typed test-data rows do not support packing individual elements into C# 13 params ReadOnlySpan<T> parameters. Packing currently supports arrays and five array-assignable collection interfaces. Support for span params would let users pass typed rows to methods using the newer C# syntax.

Reproduction

On .NET 10, declare a TypedDataSourceAttribute<(int[], string)> source and apply it to [Test] void Run<T>(T[] values, params ReadOnlySpan<string> rest). The row contains an array and one string; the desired invocation packs the string into rest.

Proposal

Support span params consistently in source-generated discovery, reflection execution and analyzer validation, or provide a specific unsupported-parameter diagnostic. Reflection invocation cannot box a span, so accepting the analyzer conversion alone is insufficient.

At main commit d9e9e66, TupleArgumentHelper.GetTrailingElementType and ReflectionTestDataCollector.GetTrailingElementType only accept arrays and IEnumerable<T>, ICollection<T>, IList<T>, IReadOnlyCollection<T>, and IReadOnlyList<T>. Both return null for ReadOnlySpan<T>.

Discovered while reviewing #7460; broader params support is outside its array-inference scope. Please handle the span parameter consistently in both execution modes.