Add non-special scheme URLs parser

This CL is separate from the main CL (https://crrev.com/c/4929491).

This CL adds a URL parser for non-special URLs.

The newly added parser functions are currently unused and will be used
in following CLs. Thus, guarding these functions by the flag is
unnecessary at this point.

As described in `url/README.md`, URL library has two layers:

1. Parsing
2. Canonicalization

This CL updates "Parsing" layer for non-special URLs.

Canonicalization of non-special URLs is a more complex task. It will be
addressed in following CLs.

Tests:

This CL adds minimal unit tests for the ParseNonSpecialURL() function.
These tests should be sufficient to verify the basic behavior of the
parser.

The WPT URL tests have a good coverage for non-special URLs and will be
used in following CLs, so I don't add much unit tests in this CL to
avoid duplication.

Bug: 1416006
Change-Id: Ibe5450ccdd4fc6d5c2386b1e838e9e254ce90308
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5028539
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Timothy Gu <timothygu@chromium.org>
Commit-Queue: Hayato Ito <hayato@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1232562}