ci: remove pip usage from CI

uv is now available from within Shrinkwrap's Docker images, which means
that all of Shrinkwrap's `pip install`-able dependencies should be
declared explicitly in `pyproject.toml`, including runtime dependencies
of the projects that Shrinkwrap builds.

Runtime dependencies have been separated out into optional dependencies.
These dependencies differ from dependency groups in that they are
available to downstream users using the "extras" syntax:

    uv tool install "git+https://

<...>/shrinkwrap.git[runtime]"

This change introduces the following extras:

  - `runtime` - runtime dependencies for all projects
  - `runtime-edk2` - runtime dependencies for EDK2
  - `runtime-op-tee` - runtime dependencies for OP-TEE
  - `runtime-tf-a` - runtime dependencies for TF-A

Signed-off-by: Chris Kay <chris.kay@arm.com>