optimize: Simplify and clean up Dockerfile

[Leke-Ariyo]

What this PR does / why we need it:
Optimizes the Dockerfile for better efficiency and readability.

Special notes for your reviewer:
Please pay attention to the Trivy installation simplification.

Details:

• Grouped related environment variables to reduce Docker layers.
• Used a case statement for Trivy installation to simplify the process.
• Removed unnecessary commands and combined related ones for efficiency.
• Added comments throughout the Dockerfile for clarity.

How to test this PR:

1. Build the Docker image using the updated Dockerfile.
2. Run the container and ensure all functionalities are working as expected.

Screenshots:
N/A

Additional context:
This optimization aims to make the Dockerfile more maintainable and efficient.

[dereknola]

@Leke-Ariyo Thank you for the community PR. Per CNCF guidelines, all commits must be signed to pass DCO. Please see https://github.com/k3s-io/k3s/pull/8244/checks?check_run_id=16194110860.

[Leke-Ariyo]

@Leke-Ariyo Thank you for the community PR. Per CNCF guidelines, all commits must be signed to pass DCO. Please see https://github.com/k3s-io/k3s/pull/8244/checks?check_run_id=16194110860.

done @dereknola

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c7c339f) 45.11% compared to head (073a172) 49.22%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #8244      +/-   ##
==========================================
+ Coverage   45.11%   49.22%   +4.11%     
==========================================
  Files         148      148              
  Lines       15674    15674              
==========================================
+ Hits         7071     7716     +645     
+ Misses       7457     6715     -742     
- Partials     1146     1243      +97     

Flag	Coverage Δ
e2etests	46.94% <ø> (?)
inttests	40.88% <ø> (-1.70%)	⬇️
unittests	17.87% <ø> (ø)

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see 50 files with indirect coverage changes

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[dereknola]

We can ignore the failure on secrets-encryption, the test is flaky and is being fixed in another PR.

[Leke-Ariyo]

We can ignore the failure on secrets-encryption, the test is flaky and is being fixed in another PR.

Thanks, sounds good @dereknola . I have committed your suggestion

[dereknola]

Looks like your new commit was signed, so you invalidated the DCO again.

[Leke-Ariyo]

Looks like your new commit was signed, so you invalidated the DCO again.

I just signed

[dereknola]

@Leke-Ariyo We are out of code freeze (last 2 months releases were back to back). Can you please rebase off master/resolve your conflicts?

[Leke-Ariyo]

looks like all is good to go, I do not have merge access

[brandond]

we are in code freeze for a +k3s2 release. Nothing is being merged until that is complete.