Expose --include-symbols and --include-source in dotnet pack task

[ryandle]

Required Information

Entering this information will route you directly to the right team and expedite traction.

Question, Bug, or Feature?
Type: feature

Enter Task Name: DotNetCoreCLIV2 (pack)

Issue Description

Expose --include-symbols and --include-source for the dotnet pack task.

A more general request is mentioned here.

I plan to submit a PR for this.

[ryandle]

I decided to also address the other issue I mentioned above in this PR:

#6567

[ghost]

@alexmullans I think this can be closed thanks(!) to @ryandle's contribution

[infin8x]

Yep, thanks.