vendor dependencies and speedup container build

[mariomac]

Having to download vendor dependencies on each build complicates the downstream compilation process. This PR vendors them.

It also slightly optimizes the container build process, separating the linting stage from the build_code stage. Having to download golangci-lint on each build made the process too slow.

Now the build time for a container is ~100seconds, which could be halved if we provided two different container images: a "production" FLP that only compiles and includes the flowlogs-pipeline binary (as we will have downstream), and a "debug" image that also includes the confgenerator, as well as the iputils, curl and net-tools packages.

[codecov-commenter]

Codecov Report

Merging #264 (8a483eb) into main (03e1e4e) will decrease coverage by 0.04%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #264      +/-   ##
==========================================
- Coverage   60.24%   60.19%   -0.05%     
==========================================
  Files          69       69              
  Lines        4095     4095              
==========================================
- Hits         2467     2465       -2     
- Misses       1466     1469       +3     
+ Partials      162      161       -1     

Flag	Coverage Δ
unittests	60.19% <ø> (-0.05%)	⬇️

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

Impacted Files	Coverage Δ
pkg/pipeline/ingest/ingest_collector.go	48.12% <0.00%> (-1.51%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 03e1e4e...8a483eb. Read the comment docs.

[github-actions]

New image: ["quay.io/netobserv/flowlogs-pipeline:dcd64a6"]. It will expire after two weeks.

[jotak]

/lgtm
About production image versus debug: maybe that's a difference we can leave between upstream and downstream (with the production image only built for downstream) ?

[eranra]

@mariomac I very much like the idea of debug vs. production ... I also had discussions with @ronensc on how to use remote debug and enablement of a specific debug container might be a good way to achieve that