Add kernel memory functions & other memory-related changes (#590)

New Features

- Added policy-based memory allocation APIs with capability flags and optional alignment: `memory_alloc_with_policy`, `memory_realloc_with_policy`, `memory_calloc_with_policy`, and `memory_free`.
- Switched heap memory reporting to `memory_print_stats`.

Bug Fixes

- Improved allocation robustness with capability fallback behavior.
- Added overflow-safe handling for aligned zero-initialized allocations.
- Tightened const-correctness for generated device-tree device arrays.

Tests

- Added unit tests for default policy, alignment, zero-initialization, realloc preservation, freeing, and memory stats reporting.

Buildscripts/DevicetreeCompiler/tests/data/expected_devicetree.h

@@ -7,10 +7,10 @@ extern "C" {
 #endif
 
 // Array of device tree modules terminated with DTS_MODULE_TERMINATOR
-extern struct DtsDevice dts_devices[];
+extern const struct DtsDevice dts_devices[];
 
 // Array of module symbols terminated with NULL
-extern struct Module* dts_modules[];
+extern struct Module* const dts_modules[];
 
 #ifdef __cplusplus
 }