Use a single shared set of CA, client & server keys/certs for testing

[rjs211]

Signed-off-by: rjs211 srivatsa211@gmail.com

Which problem is this PR solving?

• currently, there are two versions of certificates used for for testing. This is redundant

Short description of the changes

• consolidate the certificates needed for any secure client-server channel used during testing.
• Added README.md for creation of CA, client, server keys and certificates

[codecov]

Codecov Report

Merging #2343 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2343      +/-   ##
==========================================
- Coverage   95.65%   95.64%   -0.01%     
==========================================
  Files         205      205              
  Lines       10529    10529              
==========================================
- Hits        10071    10070       -1     
  Misses        392      392              
- Partials       66       67       +1     

Impacted Files	Coverage Δ
cmd/query/app/server.go	90.90% <0.00%> (-2.28%)	⬇️
plugin/storage/integration/integration.go	80.38% <0.00%> (-0.48%)	⬇️
...lugin/sampling/strategystore/adaptive/processor.go	100.00% <0.00%> (+0.79%)	⬆️

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[yurishkuro]

Nice! 🎉 🎉 🎉

[yurishkuro]

nit: trailing / not needed

[yurishkuro]

Tip: take a look at CONTRIBUTING.md for guidelines on PR/commit titles. I renamed this one.