HTTP semantic convention stability migration for Pyramid (#3982)

* wip

* Fix opt-in mode set at init

* Add tests

* Changelog

* Style

* Update CHANGELOG.md

* pyramid semconv migration

* Revise test

* Add _set_http_url to Pyramid instr

* adjust test imports

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Co-authored-by: Riccardo Magliocchetti <riccardo.magliocchetti@gmail.com>