Currently init code for SPs is run in TFM Core context (reserved for init and non-secure to secure gateway calls), which has its own PSP and sandbox.
This means that secure partition implementations have a dependency and requirement on target and TFM internal stack size allocation which in turn leads to TF-M internal code changes in the event of a secure partition inclusion/exclusion or changes to their stack requirements.

Clean up target dependencies associated with initialization and change context for SP initialization so that SP init uses the context reserved for SP execution.