Runnable buddy PR

runnable, with many logs, tests not checked yet

runnable platform:
1.qemu_virt64_aarch64

---

fix bugs:
1.multiple DRAM_BASE : kernel/src/boards/qemu_virt64_aarch64/mod.rs
2.multiple instances of BUDDY_ALLOC : kernel/src/allocator/mod.rs
3.use PHYS_DRAM_SIZE when link.x links all symbols with linearmap offset
4.buddy init code ignore kernel image part in memory layout
5.metadata_end's calculation should sub linearmap_offset first
6.buddy init code set zero [mem_start, page_array_size] directly, ignore
kernel image part

---

modified:
kernel/src/allocator/Kconfig
kernel/src/allocator/buddy/heap.rs
kernel/src/allocator/buddy/mod.rs
kernel/src/allocator/buddy/page.rs
kernel/src/allocator/buddy/tests.rs
kernel/src/allocator/mod.rs
kernel/src/boards/qemu_virt64_aarch64/config.rs : define DRAM_SIZE
kernel/src/boards/qemu_virt64_aarch64/link.x : LENGTH = 125.5M, increase linearmap region size from 32M to 125.5M
kernel/src/boards/qemu_virt64_aarch64/mod.rs : pub use DRAM_SIZE

Author: YinhuaChen-vivo

kernel/src/allocator/Kconfig

@@ -35,3 +35,13 @@ config SLAB_DYNAMIC_MAX_TOTAL_PAGES
     int "Max total pages in page pool"
     default 32
     depends on ALLOCATOR_SLAB_DYNAMIC
+
+config BUDDY_ALLOCATOR
+    bool "Enable buddy allocator as physical page manager"
+    default y
+    help
+        Enable the buddy allocator to manage all physical memory pages.
+        When enabled, slab allocator operates on top of buddy-allocated
+        page pools; >= PAGE_SIZE allocations go directly to buddy;
+        tlsf/llff keep their original __heap_start~__heap_end path.
+        When disabled, the kernel falls back to direct heap management.