Revert "Stop reading arm_use_neon, arm_version in webrtc"

This reverts commit d1767395b66860a15d55b98849603d396eac090b.

Reason for revert: WebRTC must keep WEBRTC_ARCH_ARM / WEBRTC_ARCH_ARM_V7 for a little bit longer.

Original change's description:
> Stop reading arm_use_neon, arm_version in webrtc
>
> These are always true (or >= 7) after
> https://chromium-review.googlesource.com/c/chromium/src/+/7262201
>
> Bug: chromium:469092869,webrtc:473768792
> Change-Id: I6e20227da7175f84e15d8335026f35c32c95d564
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/440080
> Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Commit-Queue: Nico Weber <thakis@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#46560}

Bug: chromium:469092869,webrtc:473768792
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Change-Id: I12d3ecccb010e6feacb8c32d7d6e4693f2271043
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/440320
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46564}