Declare fields in PatchscopeBase

[tvhong]

Notes

PatchscopeBase references the fields inside the child class Patchscope.

This breaks Intellisense. So, I'm declaring all fields inside PatchscopeBase.

Also moves the Context classes to patchscope base to avoid circular dependency

Testing

pytest passed

[shaheenahmedc]

This looks good to me. Do we need to change all imports of SourceContext and TargetContext in this PR, to account for this?

[tvhong]

Let me make obvs.patchscope a package. Then have 3 files in it: patchscope, patchscope_base, and contexts. That way, each file is small and users can still import from obvs.patchscope.

[tvhong]

I'll refactor after the FutureLens PR is merged to avoid conflict.

[shaheenahmedc]

@tvhong whenever you have some time, shall we get this merged? Haven't thought through if it will affect #48 and any scripts, but just in case

[tvhong]

Thanks for the reminder @shaheenahmedc. I'll wait for you to merge #48 & #52 and then rebase this change.