Add support for exclude by attribute

As of now, coverlet could exclude any classes/methods/properties decorated with ExcludeFromCodeCoverage attribute. However, it does not applicable for code annotated by other attributes like GeneratedCodeAttribute nor CompilerGeneratedAttribute. In short, it does not allow user to exclude with arbitrary attribute. This is one of most common feature for other coverage tool (e.g. dotcover) that I usually use.

There are already demands to this feature, as listed below:

• #194 - CompilerGeneratedAttribute
• #125 - GeneratedCodeAttribute

The feature will have the following criteria:

1. Add additional argument parameter --exclude-by-attribute for CLI tool
2. Add additional MSBUILD property ExcludeByAttribute
3. Existing implementation to exclude code annotated by ExcludeByCodeCoverage remains as is
4. Exclusion list could be arbitrary specified in multiple, delimited by ,, just like existing Exclude list.
5. Any code, i.e.: classes, properties, and methods annotated with listed attributes, will be ignored from coverage.
6. The behavior of criteria 5 above, will be similar to how existing ExcludeByCodeCoverage works.

TQ.

[amweiss]

I believe this is working as part of the build tasks now, @nordinrahman and @tonerdo is there anything left needed to merge #233 ?

[amweiss]

@nordinrahman if you can, please try to clone my PR (#233) and see if it meets your needs, it passed the basic tests but I’m struggling a bit to see good ways to test it while in development.