Allow targetProfile setting in qsharp.json

[minestarks]

Today, we allow configuring the target profile in VS Code and in Python (through qsharp.init) but there is no way to persist the profile setting along with a qsharp.json project.

We can add a new field, targetProfile to qsharp.json. The compiler, language service and Python library would respect this setting. This configuration would override the existing means of setting the target profile (VSCode setting and qsharp.init).

[cesarzc]

@minestarks if you start working on this could we sync? Before allowing that I think it would be worth considering options for targets that include "adaptive profile".

[sezna]

@cesarzc do you think it'd also be useful if we allowed a list of specific runtime capabilities, in addition to target profile presets? the target profile presets would just be a known alias of runtime capabilities, as we've discussed