Minor refactoring

[theobat]

Many things arre happening in the Execute Module, which requires a big split, like prior work, we'll have execute, executePackage, executeComponent

[mpilgrem]

@theobat, my plan is [1] to merge a couple of field namings that I have in progress, then [2] rebase this pull request against the master branch and merge it, then [3] continue with other field namings.

[theobat]

ok @mpilgrem I just rebased, but feel free to add some more renamings

[mpilgrem]

@theobat, after I merged this, I realised that it has code duplicated in Stack.Build.Execute and Stack.Build.ExecuteEnv. For example, both define and export withSingleContext. Was that the intention?

EDIT: I think I've worked out what was intended see #6420

[theobat]

@mpilgrem no the datatypes and functions exported by ExecuteEnv should only be imported in Execute and not be redefined (the code is the same, it's only a module breakup)