Fix render of literal to be rendered in codeblock

[dfireBird]

Fixes #18765.

Chose this approach to simplify finding the needed n back ticks, instead of finding the consecutive back ticks.
Tested for about 100 consecutive back ticks, it was working fine.

Regarding tests, I'll add some soon. Just wanted to review the implementation.

[dfireBird]

Added tests as part of same commit, they basically test the number of back ticks that is before and after. Nothing much can be done apart from that I guess.

[Jisu-Woniu]

What if the string consists entirely of space characters?

If the resulting string both begins and ends with a space character, but does not consist entirely of space characters, a single space character is removed from the front and back.

e.g.

`  `   (the rendered form of an empty string)
`   `  (the rendered form of string " ", or 1 space)

will become

(2 spaces) and (3 spaces)

[Veykril]

Ah indeed, fully whitespace strings we need to special case thats a good point!

[dfireBird]

We should do that, but fun thing in vscode hover renderer trims all leading and trailing spaces inside codeblock. Like even with current implementation hovering over something like r" hello " will only render hello

[Veykril]

That is unfortunate but not much we can do about then I think, ultimately markdown rendering differs from implementation to implementation. We could note down the number of leading / trailing whitespace in parenthesis after I suppose (if there are any)

[Jisu-Woniu]

Is it possible to use <code> </code> to wrap the values instead?

[dfireBird]

From my research about it, VSC only allows <span></span by default and others are sanitized. There is user config that can control it, but I'm not sure if that can be used here.