Seperate out the test dependencies from octez-libs

The following discussion from !8637 (merged) should be addressed:

• @raphael-proust started a discussion: (+4 comments)

  We should really make an effort to separate out the test dependencies. Right now on master it's an issue of p2p but with this MR you inherit the issue in octez-libs.

  I'm not sure which order of work is the most appropriate, but it's important to not forget about this.