Address param-nullchecking formatting issues

[RikkiGibson]

We have such a test for the formatter itself. It wouldn't hurt to have it for the formatting analyzer too.

roslyn/src/Workspaces/CSharpTest/Formatting/FormattingTests.cs

Lines 5779 to 5799 in 259a9e2

	[Fact]
	[Trait(Traits.Feature, Traits.Features.Formatting)]
	public async Task SpacingInNullCheckedParameter()
	{
	var code =
	@"class C
	{
	static object F(string s !!)
	{
	}
	}";
	var expectedCode =
	@"class C
	{
	static object F(string s!!)
	{
	}
	}";
	await AssertFormatAsync(expectedCode, code);
	}

I did find that we don't do the right thing in the following scenario:

static void M1(string x
    !!)
{
}

I expected !! to always be moved to be right up against the parameter name. It seems like the leading trivia owned by !! should be moved to the next token, for consistency with the following (which doesn't prompt any formatting errors)

static void M1(string x
    )
{
}

All that said, I'd prefer to back-burner this work and possibly make it "help wanted". The important thing I wanted to confirm with this PR is that "correctly formatted" code using the feature doesn't produce formatting warnings.

Originally posted by @RikkiGibson in #58936 (comment)

[jcouv]

Closing as the feature is no longer applicable.