fix: implement rfc3986 dot-segment removal and percent-encoding normalization

[gaoflow]

resolve() and normalize() each carried their own hand-written ./.. loop, and neither is the remove_dot_segments routine from rfc3986 §5.2.4. Both now call one helper transcribed from it.

A trailing . or .. segment dropped the required slash — §5.2.4 steps 2B/2C replace a final /. or /.. with /. resolve('http://a/b/c/d;p?q', '..') returned http://a/b, want http://a/b/; normalize('http://e.org/a/b/..') returned http://e.org/a, want http://e.org/a/.

A reference with its own authority inherited the base path and port — §5.2.2 does not consult the base when R.authority is defined. resolve('http://a/b/c/d;p?q', '//g') returned http://g/b/c/d;p, but the §5.4.1 table in the RFC gives "//g" = "http://g". resolve('https://a:8080/x/y', '//g/h') returned https://g:8080/h, want https://g/h.

normalize() percent-encoded valid path characters — rawurlencode(rawurldecode($segment)) escapes the 11 sub-delims plus : and @, all of which are valid pchar (§3.3), so http://a/b/c/d;p?q became http://a/b/c/d%3Bp?q and /a;b compared equal to /a%3Bb, which §2.2 says are not equivalent. The ltrim() also collapsed //a to /a and the unconditional '/'.implode() rooted rootless paths (urn:isbn:0451450523 → urn:/isbn%3A0451450523). Triplets are now upper-cased and decoded only when the octet is unreserved (§6.2.2.1, §6.2.2.2); bytes that are not pchar are still encoded, as before.

The §5.4.1 and §5.4.2 examples are now a data provider — 41 of the 42, with the empty reference left out because #145 covers it. Plus normalization vectors for the 13 characters, the trailing dot segments, %2E, empty segments and rootless paths.

Four ResolveTest rows change, all of them //example.net with no path. They arrived in 0d4c9a3 next to a ?:→?? falsiness fix for a base path of '0', and they pin the base-path inheritance above; the four sibling rows using //example.net/ are untouched, and I added two rows so a '0' base path stays covered. Cross-checked against urllib.parse.urljoin, Go net/url and Addressable — all three drop the base path for //g. phpunit, phpstan and php-cs-fixer are green locally.