fix(string): compare full URL parameter names

[Miladkhoshdel]

Problem

strip_url_params2 used only the first character of each query parameter as its key. Different parameters with the same first letter were therefore treated as duplicates.

For example:

strip_url_params2("https://x.test?ab=1&ac=2&ab=3")

Previously returned https://x.test?ab=1, incorrectly dropping ac. The expected result is https://x.test?ab=1&ac=2: ab appears twice, but ac is a separate parameter.

The previous loop also skipped the first parameter when applying param_to_strip.

Changes

• Extract the full parameter name before = for duplicate checks.
• Keep the first occurrence of each parameter, in its original order.
• Apply param_to_strip to every parameter, including the first.

Tests

Added regression cases for distinct names with a shared first letter, repeated multi-character names, and removal of the first parameter.

Ran python3 -m unittest discover -s tests -p test_string.py — all 68 tests passed.

Fixes #2773