Fix incorrect codespit of xml doc comments

[CyrusNajmabadi]

Fixes #75838

[CyrusNajmabadi]

@ToddGrun ptal

[AlmightyLks]

As I can see from the written test, the expected behaviour is going to be that it generated another broken xml-doc line, assuming it is already in a valid state given the "///", instead of checking for a proper summary-wrapped xml doc?

We already have an analyzer/code-completion that turns

/// Bla
class C { }

into

/// <summary>
/// Bla
/// </summary>
class C { }

if we remove and re-add one of the slashes in the line.

However, if we have two lines within our broken summary, like so

/// Bla
/// Bla Bla
class C { }

removing and re-adding one of the slashes will turn it into a half-fixed summary block

/// <summary>
/// Bla
/// </summary>
/// Bla Bla
class C { }

This could make sense, if the lower summary xml docs were wrapped in other / already existing xml doc tags, but they are not, thus they should always belong to the upper generated summary xml.
Those are some of my thoughts on the behaviour, and why I dont think this fix necessarily fixes the underlying issue completely

[CyrusNajmabadi]

I'm fixing the issue where the code spit is utterly wrong, duplicating code improperly.

You're welcome to submit other behavioral changes.

[ToddGrun]