page_alloc: make test fixture public

Having the ability to use the `FrameAlloctor`, simulating via the heap
is a very useful pattern when testing libkernel code. Make the test
fixture public for other modules to use.

libkernel/src/memory/page_alloc.rs

@@ -427,7 +427,7 @@ pub trait PageAllocGetter<C: CpuOps>: Send + Sync + 'static {
 }
 
 #[cfg(test)]
-mod tests {
+pub mod tests {
     use super::*;
     use crate::{
         memory::{
@@ -438,13 +438,13 @@ mod tests {
         test::MockCpuOps,
     };
     use core::{alloc::Layout, mem::MaybeUninit};
-    use std::vec::Vec; // For collecting results in tests
+    use std::{mem::ManuallyDrop, ptr, vec::Vec}; // For collecting results in tests
 
     const KIB: usize = 1024;
     const MIB: usize = 1024 * KIB;
     const PAGE_SIZE: usize = 4096;
 
-    struct TestFixture {
+    pub struct TestFixture {
         allocator: FrameAllocator<MockCpuOps>,
         base_ptr: *mut u8,
         layout: Layout,
@@ -456,7 +456,7 @@ mod tests {
         /// - `mem_regions`: A slice of `(start, size)` tuples defining available memory regions.
         ///   The `start` is relative to the beginning of the allocated memory block.
         /// - `res_regions`: A slice of `(start, size)` tuples for reserved regions (e.g., kernel).
-        fn new(mem_regions: &[(usize, usize)], res_regions: &[(usize, usize)]) -> Self {
+        pub fn new(mem_regions: &[(usize, usize)], res_regions: &[(usize, usize)]) -> Self {
             // Determine the total memory size required for the test environment.
             let total_size = mem_regions
                 .iter()
@@ -534,6 +534,12 @@ mod tests {
         fn free_pages(&self) -> usize {
             self.allocator.inner.lock_save_irq().free_pages
         }
+
+        pub fn leak_allocator(self) -> FrameAllocator<MockCpuOps> {
+            let this = ManuallyDrop::new(self);
+
+            unsafe { ptr::read(&this.allocator) }
+        }
     }
 
     impl Drop for TestFixture {