Use a single entrypoint for the datadog agent docker image

[L3n41c]

What does this PR do?

Use a single entrypoint for the datadog agent docker image.

Motivation

GKE auto-pilot requires to have a fixed entrypoint in the docker image.

Additional Notes

This new version of the operator requires an agent docker image that includes DataDog/datadog-agent#8490. It is the operator counter part of DataDog/helm-charts#289.

Describe your test plan

Spawn an agent thanks to this version of the operator once with 7.29.0 and once with 7.30.0. In the former case, we should have command: for containers in the pod spec as we’re used to. In the later case, there shouldn’t be any command: for any container anymore. It should be replaced by an ENTRYPOINT environment variable for each container.

[codecov-commenter]

Codecov Report

Merging #339 (bbeb175) into main (5a31233) will increase coverage by 0.36%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #339      +/-   ##
==========================================
+ Coverage   63.21%   63.58%   +0.36%     
==========================================
  Files          60       60              
  Lines        6606     6673      +67     
==========================================
+ Hits         4176     4243      +67     
  Misses       2126     2126              
  Partials      304      304              

Flag	Coverage Δ
unittests	63.58% <100.00%> (+0.36%)	:arrow_up:

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
controllers/datadogagent/utils.go	83.52% <100.00%> (+0.79%)	:arrow_up:
pkg/utils/version.go	71.42% <100.00%> (ø)

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