refactor(processor): stop using global variables

[atzoum]

Description

Preparation steps before starting the actual work for introducing workspace isolation in processor:

• Removing global variables from the processor package
• Renaming processor.HandleT to processor.Handle
• Introducing misc.AsyncInit for streamlining how our components wait for their proper initialization before actually starting working (hint: backendconfig.WaitForConfig is not 100% safe)
• Make sure that processor is properly initialized before starting (using misc.AsyncInit)
• Fix issue with multiple successful HTTP requests performed for transformer features when starting up

Notion Ticket

Link

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[codecov]

Codecov Report

Base: 49.66% // Head: 49.54% // Decreases project coverage by -0.13% ⚠️

Coverage data is based on head (e37ab56) compared to base (44691c3).
Patch coverage: 86.66% of modified lines in pull request are covered.

❗ Current head e37ab56 differs from pull request most recent head 138fbc2. Consider uploading reports for the commit 138fbc2 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2881      +/-   ##
==========================================
- Coverage   49.66%   49.54%   -0.13%     
==========================================
  Files         316      315       -1     
  Lines       50433    50108     -325     
==========================================
- Hits        25048    24826     -222     
+ Misses      23853    23765      -88     
+ Partials     1532     1517      -15     

Impacted Files	Coverage Δ
processor/transformqueue.go	79.41% <ø> (+8.35%)	⬆️
runner/runner.go	70.61% <ø> (+0.22%)	⬆️
processor/trackingplan.go	53.38% <66.66%> (ø)
processor/manager.go	94.00% <84.61%> (+0.66%)	⬆️
processor/processor.go	86.15% <86.95%> (-0.22%)	⬇️
utils/misc/asyncinit.go	88.00% <88.00%> (ø)
...ger/transformation/transformationStatusUploader.go	24.24% <0.00%> (-14.61%)	⬇️
testhelper/log/log.go	7.69% <0.00%> (-3.85%)	⬇️
services/rsources/handler.go	73.82% <0.00%> (-1.38%)	⬇️
... and 24 more

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[fracasula]

It looks like WaitContext is used in tests only. Why not use a WaitGroup instead of creating this new AsyncInit type?

[atzoum]

Using a wait group was my initial approach, but WaitGroup#Wait is a blocking call, whereas listening from a channel doesn't have to be. Consider this as a WaitGroup using a channel for communicating completion instead of blocking.

[fracasula]

Makes sense, it's not too complex either so 👍