Clean opam, poetry and npm caches

Tezos/tezos: tezos!9322 (merged)

This:

• cleans the opam cache after install in runtime-build-dependencies (saving ~1.3GB)
• cleans the poetry/pip cache after install in runtest-build-test-dependencies (saving ~60MB)

In total, this reduces the size of the e2etest image from 6.2GB to 4.8GB. Still huge 🤷

You can inspect the images using dive.

Before:

dive registry.gitlab.com/tezos/opam-repository:runtime-build-e2etest-dependencies--amd64--452214cb12f8fdd5b5a2a6f77f330fc0bfd78740

After:

dive registry.gitlab.com/tezos/opam-repository:runtime-build-e2etest-dependencies--amd64--3fbd2fb137d09a12cdf21ddbe5632216461fb713