fix: delayed start logic for deterministic image

[matteriben]

The previous check could fail if the clock was stepped.

Description:

Fixes problem with delayed start logic for deterministic image. Previous logic relied on start time of pid 1. However, if the system clock was stepped apparent start time of pid 1 can change subsequently preventing the service from starting correctly.

This change replaces file/time based check for initial start with a logical check based on s6 wantedup semantics. Initially wantedup will be true for this service until the service is configured not to restart on line 10.

Related issue(s):

Fixes #18264

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

@@           Coverage Diff           @@
##             main   #18265   +/-   ##
=======================================
  Coverage        ?   69.36%           
  Complexity      ?    23153           
=======================================
  Files           ?     2631           
  Lines           ?   100254           
  Branches        ?    10356           
=======================================
  Hits            ?    69543           
  Misses          ?    26751           
  Partials        ?     3960           

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[rbarker-dev]

Mirrored PR here: #19070

[matteriben]

Moved to PR#19126.