Remove/merge/adapt to Roslynator all new Visual Studio 2019 refactorings

[FrancescoBonizzi]

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Product and Version Used: 2.1.0 for VS 2019 (Preview)

Steps to Reproduce: Just the first example that comes to my mind: define a class in which a private field should be readonly because you assign it only in its class constructor:

With this class:

Actual Behavior:

• VS2019 suggests you to "Add readonly modifier" IDE044
• Roslynator suggest you to "Mark _abc as readonly" RCS1169

Expected Behavior: Just show one of the two, and like this for all duplicated refactorings

[Danghor]

This seems to be a duplicate of #227 and #371 (#460 is also somewhat related)

[Danghor]

So here is what I found so far. I will edit this note when I find more duplicates.

Roslynator	Visual Studio	Description in Roslynator	Description in Visual Studio
RCS1058	IDE0054	Use compound assigment.
RCS1085	IDE0032	Use auto-implemented-property.	Use auto property
RCS1163	IDE0060	Unused parameter '{0}'.
RCS1169	IDE0044	Make field read-only.	Make field readonly
RCS1206	IDE0031	Use conditional access instead of conditional expression.
RCS1213	IDE0051	Remove unused method declaration.
RCS1221	IDE0019	Use pattern matching instead of combination of 'as' operator and null check.