Branch coverage support

[rodrigo-speller]

Changes proposed in this pull request:

• Set CoverageResult.Batches as public. This allow generate other reports using SQLCover as library.
• Refactory of CoverageResult.OpenCoverXml to use an serializer (OpenCoverXmlSerializer). Use it to SRP and for most readable code.
• Branch coverage support!!!

How to test this code:

• Create procedures with While and If blocks and generate the OpenCover report.

Has been tested on (remove any that don't apply):

• SQL Server 2017

[lastlink]

I would add unit tests or make sure this builds, github actions now works w/ integrated db tests, see .github/ .yml file

If you look at the yml I use the dotnet tool reportgenerator to generate teh OpenCover html reports using the existing .xml. If this still works after your change it might be fine then.

also you need to update to handle the pr recently that moved things to a share library using the dotnet standard