Allow running php system tests with self-compiled artifact

[bwoebi]

I.e. with only the ddtrace.so and the src/ for the php source files.

E.g. for parametric, needing 8.2, in dd-trace-php repo:

# To get the php binary
docker compose run --rm 8.2-bookworm bash
switch-php nts
make install

# on other shell, to copy
rsync -a src/ ~/system-tests/binaries/src/
docker cp $(docker ps | grep 8.2-bookworm | rev | cut -d" " -f 1 | rev):/opt/php/nts/lib/php/extensions/no-debug-non-zts-20220829/ddtrace.so ~/system-tests/binaries/

And then they can be run easily locally, without involving CI to produce a full artifact.

[github-actions]

CODEOWNERS have been resolved as:

docs/execute/binaries.md                                                @DataDog/system-tests-core
utils/_context/_scenarios/parametric.py                                 @DataDog/system-tests-core
utils/build/docker/php/common/install_ddtrace.sh                        @DataDog/apm-php @DataDog/system-tests-core