Allow overriding cft settings within individual blocks

It's a reasonable use case to want to configure `cft` _differently_ in separate groups of tests. For example, in test frameworks that use `describe("name", () => ...` blocks, having a single `describe` block allow a particular console method (#35 / #36) would be good.

I think this would imply there needs to be a stack of configurations with abstracted ways to push & pop from it... Haven't done much digging yet. It'd be great to see a proposal here!

The issue does not identify files, tests, or an entry point; begin by examining how cft currently stores configuration and how test-framework blocks are integrated. Propose a configuration push/pop design for separate describe blocks, including how console methods are overridden and restored; no acceptance criteria are specified.

Written by the indexing model from the issue text.