Cleanup arraysize usage in //net

When/where appropriate, the following conversions are made:
- Range-based for loops when iterating
- constexpr base::StringPiece for string constants
- base::span<> for array types
- base::size() as last resort

Bug: 837308
Change-Id: I7cb5ef94220049cfad935e9719657402461ff53d
Reviewed-on: https://chromium-review.googlesource.com/1056111
Commit-Queue: Ryan Sleevi <rsleevi@chromium.org>
Reviewed-by: Eric Roman <eroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#558588}
28 files changed