Fix1914 - Variable substitution stopped working with release 1.7

[andreeis]

Fix1914 - Variable substitution stopped working with release 1.7, related to sourceDirectory and kit info variables. https://github.com/microsoft/vscode-cmake-tools/issues/1914

Will add explanations later, do more cleanup and also ensure more variables are considered. For now, just kit name and vendor, two examples that are different and exist in different data structures. Creating the PR to see tests outcome.

[andreeis]

The last PR update does the following:

• error when presets are on and user still has kit variables to expand. we don't expand even if, with presets off, we have all info available saved in the project state
• fix wrong assumption in the previous approach: we can't expand the generator name variable in sourceDir. Generator deduction depends on configure which depends on sourceDir. So we error if sourceDir contains generator variable.