refactor(vmm builder): to simplify logic that creates the microVM to …

…boot

Streamline the event_manager to avoid passing it through unnecessary
functions, isolating the code with distinct architectural designs.
Consolidate architecture-specific configurations exclusively within the
build_microvm_for_boot and build_microvm_from_snapshot functions for
clarity and efficiency.

Signed-off-by: tommady <[email protected]>