[uss_qualifier] Add execution control

[BenjaminPelletier]

With uss_qualifier's configurations growing larger, there is often a need to focus execution on a smaller part of the final configuration for the purpose of rapid development. Currently, users must create a new configuration sufficiently similar to the final configuration to accomplish this, and this can be, tedious, error-prone, and time-consuming.

This PR introduces execution control to uss_qualifier by allowing users to adjust their existing configurations only slightly in order to selectively execute only parts of the normal test run. This includes, for instance, targeting a particular scenario, a particular instance of a particular scenario, or a test suite, or excluding the same. As such, the configurations exercising particular components of the F3548-21 test suite in the configurations/f3548 folder are now obsolete and are removed.

Execution control is accomplished by an additional execution parameter in the TestConfiguration object; see configuration.py for its structure. The addition of this configuration field results in auto-generating a number of schema (the JSON files in this PR are all autogenerated).

Implementation of this functionality is in suite.py where a new ExecutionContext object is added. It is similar to the stack in normal programming languages, as it keeps track of what is running and has been run. The logic for whether to skip a particular action is the bulk of ExecutionContext's code.

This new functionality is documented with a number of examples in configurations/README.md.

A number of small bugs and improvements discovered while exercising this functionality are addressed.

All of the examples were tested by inserting the execution content shown into the configurations.dev.uspace configuration.

[barroco]

Looks good to me 👍