PA: Remove the usage of base::StrongAlias from allocator shims

Replaces base::StrongAlias with partition_alloc::internal::base::.

Bug: 1337681
Change-Id: Id6a80366d11f46a222bcf7cbeab90a42ce06703a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4562363


Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Takashi Sakamoto <tasak@google.com>
Reviewed-by: Bartek Nowierski <bartekn@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1149131}