partition_alloc: Follow-up moving tests.

This is a follow-up to:
https://chromium-review.googlesource.com/c/chromium/src/+/5678723

This patch fixes two errors:

Error 1:
========

The (use_partition_alloc) and (is_ios) block got merged mistakenly.

Fix was merging them back. Subsequently, I found the test could be move
toward partition_alloc as well, simplifying base.

Error 2:
========

partition_alloc provides test support only when `build_with_chromium` is
true. They are used by "base". I assumed `build_with_chromium` was true
in this context.

We have the following dependencies (current + future):
┌────────────────┐
│partition_alloc │
└┬─┬──────┬─┬─┬─┬┘
 │┌▽─────┐│ │ │┌▽─────────┐
 ││dawn  ││ │ ││base      │
 │└┬───┬─┘│ │ │└┬──────┬──┘
┌▽─▽──┐│  │ │ │┌▽─────┐│
│angle││  │ │ ││webrtc││
└┬─┬──┘│  │ │ │└┬─────┘│
 │┌▽───▽──▽┐│ │ │      │
 ││skia    ││ │ │      │
 │└┬─┬─────┘│ │ │      │
 │ │┌▽──────▽┐│ │      │
 │ ││pdfium  ││ │      │
 │ │└┬───────┘│ │      │
┌▽─▽─▽────────▽─▽──────▽┐
│chrome                 │
└───────────────────────┘

This is an occurrence where base is built without chromium.

The fix was to remove "build_with_chromium" check for ":test_support".

Fixed: 351784266
Bug: 351784266
Change-Id: If0444d1c8d2c20c98e4db1573c684821af5136b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5685192
Reviewed-by: danakj <danakj@chromium.org>
Auto-Submit: Arthur Sonzogni <arthursonzogni@chromium.org>
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1325006}
NOKEYCHECK=True
GitOrigin-RevId: 11e42da121ba8b047e34cff7f02054235ee668d8
2 files changed