Reland "align skvx::Vec<N,T> to N*sizeof(T)"
Reland "align skvx::Vec<N,T> to N*sizeof(T)"

This is a reland of e3b110dc6e5f7e1c2bdeb16d4d0ca03221c5ee25

PS1 is the original, so best to diff against that.
This is the original with compiler workarounds.

Original change's description:
> align skvx::Vec<N,T> to N*sizeof(T)
>
> This increases the alignment of these vector types.  I would have liked
> to keep the alignment minimal, but it's probably no big deal either way.
>
> In terms of code generation, it doesn't make much difference for x86 or
> ARMv8, but it seems hugely important for good ARMv7 NEON code.  It's a
> ~10x difference for the bench I've been playing around with that spends
> most of its time in that SkOpts::blit_row_color32 routine.
>
> Bug: chromium:952502
> Change-Id: Ib12caad6b9b3f3f6e821ed70bfb57099db37b15f
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208581
> Commit-Queue: Michael Ludwig <michaelludwig@google.com>
> Reviewed-by: Michael Ludwig <michaelludwig@google.com>
> Auto-Submit: Mike Klein <14574f09dfa9b4e14759b88c3426a495a0e627b0@google.com>

Bug: chromium:952502
Cq-Include-Trybots: skia.primary:Test-Win2016-MSVC-GCE-CPU-AVX2-x86-Release-All,Build-Debian9-GCC-mips64el-Debug
Change-Id: Ief99e14ab4de5a56840ed6bb326cf7669c51dc97
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/208681
Reviewed-by: Mike Klein <14574f09dfa9b4e14759b88c3426a495a0e627b0@google.com>
Commit-Queue: Mike Klein <14574f09dfa9b4e14759b88c3426a495a0e627b0@google.com>

aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,rubenvb/skia,HalCanary/skia-hc,google/skia,rubenvb/skia,HalCanary/skia-hc,rubenvb/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,google/skia,google/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,rubenvb/skia,rubenvb/skia,rubenvb/skia,HalCanary/skia-hc,aosp-mirror/platform_external_skia,HalCanary/skia-hc,google/skia,rubenvb/skia,aosp-mirror/platform_external_skia,HalCanary/skia-hc,HalCanary/skia-hc,rubenvb/skia,aosp-mirror/platform_external_skia