CI: Install deps once and then cache

[AlejandroCabeza]

Currently, installing dependencies is a step in a job that is ran multiple times. That means that, depending on concurrency, it might be run multiple times. This also includes building the p2p daemon and go.

Moving it to a job that is ran before the matrix-test-job (base_tests.yml:jobs:test) and caching the installation would save a bit of time.

This includes p2pd, dependencies installed with nimble install, etc.