[DanglingPtr] Cherry-pick upstream build failure fix

I had to spend some significant bysecting this and it turns out rust
tools don't support sanitisers, which was breaking the experimental
build with dangling pointers.

Chromium change:
https://chromium.googlesource.com/chromium/src/+/b250fcef54d8631d6fc09d1936980fa81ccaf4d0

commit b250fcef54d8631d6fc09d1936980fa81ccaf4d0
Author: danakj <[email protected]>
Date:   Tue Oct 1 17:57:51 2024 +0000

    Disable PA-based features in the Rust host tools toolchain (proc macros)

    If the user explicitly turns on ASAN and use_raw_ptr_asan_unowned_impl
    we don't want to use those in the host tools toolchain. Elsewhere we
    disable ASAN in the toolchain in build/config/sanitizers/sanitizers.gni:
    ```
    if (!is_a_target_toolchain || toolchain_for_rust_host_build_tools) {
      is_asan = false
    ```

    But that leaves use_raw_ptr_asan_unowned_impl on without ASAN which then
    causes GN assertions and badness.

    The rust host tools toolchain should just use default allocators anyway
    so that the proc macro DLLs use the same allocator as the compiler that
    dlopens them.

    Bug: 40212971

patches/base-allocator-partition_allocator-partition_alloc.gni.patch

@@ -0,0 +1,15 @@
+diff --git a/base/allocator/partition_allocator/partition_alloc.gni b/base/allocator/partition_allocator/partition_alloc.gni
+index 2b589ddd153214e237c1028f6be736351754a6f0..f320b815d1a500dffc299471140a21ff2e5d03c7 100644
+--- a/base/allocator/partition_allocator/partition_alloc.gni
++++ b/base/allocator/partition_allocator/partition_alloc.gni
+@@ -284,7 +284,9 @@ stack_scan_supported =
+ # - has_memory_tagging
+ if (!use_partition_alloc ||
+     (defined(toolchain_allows_use_partition_alloc_as_malloc) &&
+-     !toolchain_allows_use_partition_alloc_as_malloc)) {
++     !toolchain_allows_use_partition_alloc_as_malloc) ||
++    (defined(toolchain_for_rust_host_build_tools) &&
++     toolchain_for_rust_host_build_tools)) {
+   use_partition_alloc_as_malloc = false
+   glue_core_pools = false
+   enable_backup_ref_ptr_support = false