Refactor Lua balancer

[ElvinEfendi]

What this PR does / why we need it:
I've included lua-resty-balancer library at #2385 which comes with Round-Robin load balancing implementation. The PR replaces the existing RR implementation with the one from that library. And also moves chash wrapper into rootfs/etc/nginx/lua/balancer/resty.lua together with round-robin.

In a separate PR I'll cleanup balancer.lua further - don't want to make this PR too big.

Which issue this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged): fixes #
n/a

Special notes for your reviewer:
n/a

[ElvinEfendi]

/assign @aledbf

[aledbf]

/approve

[aledbf]

@ElvinEfendi I restarted the CI job several times so it seems the e2e error is real

[ElvinEfendi]

I restarted the CI job several times so it seems the e2e error is real

@aledbf yes, I can generate it locally too - debugging it now.

[codecov-io]

Codecov Report

Merging #2472 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master   #2472      +/-   ##
=========================================
- Coverage   41.61%   41.6%   -0.02%     
=========================================
  Files          74      74              
  Lines        5291    5290       -1     
=========================================
- Hits         2202    2201       -1     
  Misses       2792    2792              
  Partials      297     297

Impacted Files	Coverage Δ
internal/ingress/controller/template/template.go	65.45% <ø> (-0.08%)	⬇️
internal/file/bindata.go	62.4% <100%> (ø)	⬆️

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[ElvinEfendi]

/lgtm

[k8s-ci-robot]

@ElvinEfendi: you cannot LGTM your own PR.

In response to this:

/lgtm

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[aledbf]

/lgtm

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aledbf, ElvinEfendi

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