Include terminating line in folding ranges when last token has no trailing non-trivia

[DanielRosenwasser]

With microsoft/typescript-go#2772 (b81c7e9), we added support for lineFoldingOnly clients by consistently backing off a line; however, having a trailing } for every outlining span feels kind of unnecessary.

microsoft/vscode#3352 has a lot of feedback, so maybe we can find a compromise. We discussed this a bit at #334371.

Instead of always backing off at these brace characters, maybe we should determine whether the terminating line has any non-trivia.

In other words...

else on line following }:

A-START | if (Math.random()) {
        |
A-END   | }
B-START | else if (Math.random()) {
        |
B-END   | }

else on same line as }:

A-START | if (Math.random()) {
A-END   |
B-START | } else if (Math.random()) {
        | 
B-END   | }

Statement on same line as }

A-START | if (Math.random()) {
A-END   |
        | } /*strange, but valid*/ console.log("hi there what're you doin' on this line?")

Contents on lines following }

A-START | if (Math.random()) {
        |
A-END   | }
        | /* Normal - this is totally normal code! That is why I am saying so! */
        | console.log("Hello world!");

Empty statement on same line as }

This one is odd, and maybe even undesirable - but I anticipate the implementation will be cleaner without any special-cases.

A-START | if (Math.random()) {
A-END   |
        | };

Comment on same line as }

A-START | if (Math.random()) {
        |
A-END   | } // finally out of that `if`

End-of-file is on the same line as }

A-START | if (Math.random()) {
        |
A-END   | } <EOF>

Should ensure that we have a test where EOF is on the same line and it works fine.