Re-write wpt/cookies/http-state/ path tests

This also adds support for sending multiple Set-Cookie strings
to the test infrastructure.

Notes for history books (and reviewers)
legacy test => ported test cookie name map (ignoring Path)
path0001 => (path.html) testA=11; testB=11
path0002 => (path.html) testB=12; testA=12
path0003 => (path.html) testA=13; testB=13
path0004 => (path.html) testB=14; testA=14
path0005 => (path.html) test=15
path0006 => (path.html) test=16
path0007 => (path-redirect.html) test=1
path0008 => (path-redirect.html) test=9
path0009 => (path-redirect.html) test=10 (can be improved)
path0010 => (path-redirect.html) test=2
path0011 => (path-redirect.html) test=11
path0012 => (path-redirect.html) test=12
path0013 => (path-redirect.html) test=13
path0014 => (path-redirect.html) test=17
path0015 => not ported, see note below.
path0016 => (path-redirect.html) test=3
path0017 => (path-redirect.html) test=4
path0018 => (path-redirect.html) test=14 (can be improved)
path0019, dupe of (path.html) test1, not ported
path0020, dupe of (path.html) test2, not ported
path0021, dupe of (path.html) test3, not ported
path0022 => (path.html) test=17
path0023 => (path.html) test=18
path0024 => (path-redirect.html) test=15
path0025 => (path-redirect.html) test=16
path0026 => (path-redirect.html) test=5
path0027 => (path-redirect.html) test=6
path0028 => (path-redirect.html) test=7a
disabled-path0029 (path-redirect.html) test=7b
path0029 => (path.html) test=19
path0030 => (path.html) test=21
path0031 => path.html test=20
path0032 => (path-redirect.html) test=8a; test=8b

Notes:
For path0027 and path0028, I'm swapping the assertions (to expected a cookie) because Firefox, Safari and Chrome do this.

path0015 isn't possible to port with current WPT infra (as there are no dynamic handlers, and '/' is treated as a directory "mount").
https://bugs.chromium.org/p/chromium/issues/detail?id=1161544 is filed to track that work, and a few improvements to better capture
the intents of path0009 and path0018.


Bug: 1159925
Change-Id: I37da066e60d79e3f99e01a7d6ccbc408f447e01b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2598139


Commit-Queue: Mike Taylor <miketaylr@chromium.org>
Reviewed-by: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839497}