PersistedExecutionPointer's EventName and EventKey are shorter than PersistedEvent's ones

[vladimir-kovalyuk]

Describe the bug
EventName and EventKey properties of PersistedExecutionPointer are attributed as MaxLength(100), same properties of PersistedEvent are attributed as MaxLength(200).
When WFC attempts to save event name and event key to ExecutionPointer in WaitFor() operation that are the same as in PublishEvent() and exceed 100 symbols execution fails with error 'SQL Server Error : String or binary data would be truncated'.
At that PublishEvent is successful.

Expected behavior
PublishEvent() and WaitFor() should behave consistently so MaxLength on both PersistedExecutionPointer and PersistedEvent should be aligned and be at least 200 (taking into account production data).

[vladimir-kovalyuk]

@danielgerlag I'll prepare PR soon. But I'm stuck a bit with fixing it as we currently unable to migrate to .Net 5 (stuck on 4.6.2) so fixing EF5 migrations in WorkflowCore.Persistence.SqlServer does not seem as a fix for us.
Our workaround would be to fix it manually on DB. But how to fix it in general for 4.x .Net?

[vladimir-kovalyuk]

@danielgerlag please have a look #908 .
I created EF migration by targeting .Net 5 in WorkflowCore.Persistence.SqlServer. It didn't work out of the box.
I had to comment out the following lines in .csproj:

  <ItemGroup>
    <DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.DotNet" Version="1.0.0-msbuild3-final" />
  </ItemGroup>

Maybe .csproj should reference the package with such name but appropriate version?
Please also note that I had to change the name of docker image as I hadn't found the one the source code refers.