feat: implement configure_protection and map_shared with real page mapping, remove dead context_switch from Platform trait

crates/platform/src/lib.rs

@@ -1,6 +1,6 @@
 #![no_std]
 
-use domain::{memory::MemoryRegion, thread::SavedContext};
+use domain::memory::MemoryRegion;
 use types::{
     address::{EntryPoint, PhysicalAddress, StackPointer},
     bounded::PageCount,
@@ -9,11 +9,8 @@ use types::{
     time::{Ticks, TimerDuration},
 };
 
-pub trait PlatformContext: Copy + Default {}
-
 pub trait Platform {
     fn configure_protection(&mut self, process: ProcessId, regions: &[MemoryRegion]);
-    fn context_switch(&mut self, from: &mut SavedContext, to: &SavedContext);
     fn enable_user_mode(&mut self, entry: EntryPoint, stack: StackPointer) -> !;
     fn set_timer(&mut self, duration: TimerDuration);
     fn current_ticks(&self) -> Ticks;