logging: start Alloy after dynamic hostname setter when enabled

[everton-dematos]

Description of Changes

This PR fixes an issue where net-vm logs were missing in Grafana, while logs from other VMs on the same device were still present (https://jira.tii.ae/browse/SSRCSP-7542).

In net-vm, the hostname is set dynamically and is later exposed by journald as __journal__hostname, which is used by alloy.service to label and ship logs. In some cases, alloy.service was starting before the dynamic hostname was set, leading to inconsistent or missing net-vm logs when filtering by machine/device identifier.

To avoid this race, alloy.service is now started after the dynamic hostname setter service, but only when that service is enabled.

Type of Change

• New Feature
• Bug Fix
• Improvement / Refactor

Related Issues / Tickets

https://jira.tii.ae/browse/SSRCSP-7542

Checklist

• Clear summary in PR description
• Detailed and meaningful commit message(s)
• Commits are logically organized and squashed if appropriate
• Contribution guidelines followed
• Ghaf documentation updated with the commit - https://tiiuae.github.io/ghaf/
• Author has run make-checks and it passes
• All automatic GitHub Action checks pass - see actions
• Author has added reviewers and removed PR draft status

Testing Instructions

Applicable Targets

• Orin AGX aarch64
• Orin NX aarch64
• Lenovo X1 x86_64
• Dell Latitude x86_64
• System 76 x86_64

Installation Method

• Requires full re-installation
• Can be updated with nixos-rebuild ... switch
• Other:

Test Steps To Verify:

1. Log into net-vm
2. Generate any traceable log:
   2.1. [ghaf@ghaf-0013702975:~]$ logger "testing this PR"
3. Search on Grafana for the log
   3.1. Plese note that the host on Grafana should be set as the dynamic hosname (e.g., ghaf-0013702975)
   3.2. You should be able to visualize all the logs from net-vm (using the dynamic hostname), including the new generated log: