Fix tuple pattern matching in AotConverterGenerator to use ValueTuple types

[Copilot]

The AotConverterGenerator was generating incorrect pattern matching code for tuple types, causing compilation errors when using implicit operators with tuple parameters.

Problem

When generating AOT converters for implicit operators that accept tuple parameters like (int Value1, int Value2), the generator was creating positional patterns:

if (value is (int Value1, int Value2) typedValue)
{
    return (Foo)typedValue;
}

This syntax is interpreted as a positional pattern that looks for a Deconstruct method on the object type, which doesn't exist, resulting in compilation errors:

CS1061: 'object' does not contain a definition for 'Deconstruct'
CS8129: No suitable 'Deconstruct' instance or extension method was found for type 'object'

Solution

The fix detects when the source type is a tuple type using IsTupleType and generates the correct ValueTuple<T1, T2, ...> pattern matching syntax instead:

if (value is global::System.ValueTuple<int, int> typedValue)
{
    return (Foo)typedValue;
}

This works correctly because it pattern matches against the actual underlying ValueTuple type rather than using tuple literal syntax that gets interpreted as a positional pattern.

Example

This code now compiles successfully:

public record Foo
{
    public static implicit operator Foo((int Value1, int Value2) tuple) => new();
}

public class Tests
{
    [Test]
    [MethodDataSource(nameof(Data))]
    public void Test1(Foo data) { }

    public static IEnumerable<Foo> Data() => [new()];
}

The fix handles tuple types of any arity (2-tuple, 3-tuple, etc.) and maintains backward compatibility with existing non-tuple conversion operators.

Fixes #2798.

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[Brokolis]

I believe this can be fixed in a more clean/less manual way by creating a special SymbolDisplayFormat instead of trying to build the display type manually:

public static readonly SymbolDisplayFormat FullyQualifiedGenericWithGlobalPrefixForPatternMatching = FullyQualifiedGenericWithGlobalPrefix
    .AddMiscellaneousOptions(SymbolDisplayMiscellaneousOptions.ExpandValueTuple);

This display type can then be used for any type that will be used in pattern matching, so there is no need to handle ValueTuple specially. This SymbolDisplayFormat gives me these results (tested on Microsoft.CodeAnalysis.CSharp version 4.14.0):

For (int Value1, int Value2):

global::System.ValueTuple<int, int>

For (int, int, int, int, int, int, int, int, int, int, int, int, int, int) tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14):

global::System.ValueTuple<int, int, int, int, int, int, int, global::System.ValueTuple<int, int, int, int, int, int, int>>

For int:

int

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For reference, FullyQualifiedGenericWithGlobalPrefix gives me these results:

For (int Value1, int Value2):

(int Value1, int Value2)

For (int, int, int, int, int, int, int, int, int, int, int, int, int, int) tuple = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14):

global::System.ValueTuple<int, int, int, int, int, int, int, (int, int, int, int, int)>

For int:

int