xunit: define codefixes for TypeAsserts

[Meir017]

The asserts defined in https://github.com/xunit/assert.xunit/blob/main/TypeAsserts.cs

• IsAssignableFrom(object? @object) add support for xunit TypeAsserts IsAssignableFrom #238
• IsAssignableFrom(Type expectedType, object? @object) add support for xunit TypeAsserts IsAssignableFrom #238
• IsNotAssignableFrom(object? @object) add support for xunit TypeAsserts IsNotAssignableFrom #239
• IsNotAssignableFrom(Type expectedType, object? @object) add support for xunit TypeAsserts IsNotAssignableFrom #239
• IsType(object? @object) add support for xunit TypeAsserts IsType #240
• IsType(Type expectedType, object? @object) add support for xunit TypeAsserts IsType #240
• IsNotType(object? @object) add support for xunit TypeAsserts IsNotType #241
• IsNotType(Type expectedType, object? @object) add support for xunit TypeAsserts IsNotType #241

[Meir017]

// Xunit
XunitAssert.IsType<string>("foo");
XunitAssert.IsType(typeof(string), "foo");

// FluentAssertions
"foo".Should().BeOfType<string>();
"foo".Should().BeOfType(typeof(string));

// Xunit
XunitAssert.IsNotType<string>("foo");
XunitAssert.IsNotType(typeof(string), "foo");

// FluentAssertions
"foo".Should().NotBeOfType<string>();
"foo".Should().NotBeOfType(typeof(string));

// Xunit
XunitAssert.IsAssignableFrom<string>("foo");
XunitAssert.IsAssignableFrom(typeof(string), "foo");

// FluentAssertions
"foo".Should().BeAssignableTo<string>();
"foo".Should().BeAssignableTo(typeof(string));