[meziantou]

Fixes the open fuzzing issues, where a code fix was registered but applying it left the code unchanged.

• MA0204 ([Fuzzing] MA0204 (RemoveUnnecessaryPartialModifierFixer) registers a code fix that does not change the code #1743): when partial was not the last modifier (partial public class), the fixer called Remove(partialKeyword) on the list returned by Replace, whose tokens are not equal to the original ones, so nothing was removed. It now removes the modifier by index.
• MA0146 ([Fuzzing] MA0146 (ValidateUnsafeAccessorAttributeUsageFixer) registers a code fix that does not change the code #1742): Name = without a value is reported by the analyzer (no constant name), but the fixer found a Name argument and returned the document unchanged. The fixer now validates that the attribute exists and has no Name argument before registering the fix.
• MA0177 ([Fuzzing] MA0177 (UseInlineXmlCommentSyntaxWhenPossibleFixer) registers a code fix that does not change the code #1741): when the start or end tag spans multiple lines, the rewrite keeps the tags as-is, so the result was identical. CreateInlineElement (shared by the analyzer and the fixer) now returns null in this case, so the element is no longer reported. Documented in docs/Rules/MA0177.md.

Each fix has a regression test that fails without the fix. The tests of the three rules pass on all Roslyn versions (4.8, 4.14, 5.0, 5.6, 5.9), and the fuzz inputs no longer reproduce.

Fixes #1741
Fixes #1742
Fixes #1743