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.c

@@ -50,7 +50,7 @@ static struct Device bool_test_device = {
 	.internal = NULL
 };
 
-struct DtsDevice dts_devices[] = {
+const struct DtsDevice dts_devices[] = {
 	{ &root, "test,root", DTS_DEVICE_STATUS_OKAY },
 	{ &test_device, "test,generic-device", DTS_DEVICE_STATUS_OKAY },
 	{ &bool_test_device, "test,bool-device", DTS_DEVICE_STATUS_OKAY },
@@ -59,7 +59,7 @@ struct DtsDevice dts_devices[] = {
 
 extern struct Module data_module;
 
-struct Module* dts_modules[] = {
+struct Module* const dts_modules[] = {
 	&data_module,
 	NULL
 };