Set the priority of `system.stateVersion` between `mkDefault` and
`mkOptionDefault`.
Since this is set unconditionally for test instrumentation purposes, and
it is specifically set to:
```
Squelch warning about unset system.stateVersion
```
it should be no problem to not conflict if someone if setting this
option as `mkDefault`.
Split tests up based on certain use cases:
- http01-builtin: Tests most functionality of the core module, such
as the systemd and hashing components, whilst utilising lego's built
in http01 resolution mechanis.
- dns01: Tests only that DNS01 renewal works as expected.
- nginx: Tests nginx compatability
- httpd: Tests httpd compatability
- caddy: Tests caddy compatability
Over time, we added a lot of setup services to the ACME module, namely:
- acme-selfsigned-ca.service: Creates the selfsigned CA certificates
used to generate selfsigned certs for each configured cert.
- acme-fixperms.service: Ensures permissions correctness on certs after
system configuration changes.
- acme-lockfiles.service: Create lockfiles used to implement
maxConcurrentRenewals.
These numerous setup services complicated the dependency chain for any
cert renewal, and also made it difficult to track responsibility for
specific setup steps, for example, creating /var/lib/acme or setting
permissions of shared folders.
This change proposes a new acme-setup.service which encapsulates the
functionality of the previous 3 services into one. The service is still
defined in 3 separate chunks (using lib.mkMerge) which allows us to
keep a logical separation between each step and preserve some
optionality in the features.
The result is a generally simplified definition of systemd unit
dependencies and an obvious entrypoint for future setup extensions.
