chore: remove Init and exported struct variables from Archiver

[achettyiitr]

Description

• Remove archive.Init()
• Expose archive.New(...) to initialize.
• Remove Globals.

Linear Ticket

• https://linear.app/rudderstack/issue/PIPE-117/warehouse-init-cleanup

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

Patch coverage: 67.74% and project coverage change: +0.04% 🎉

Comparison is base (06477fc) 68.10% compared to head (f1c3ac1) 68.14%.
Report is 5 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3735      +/-   ##
==========================================
+ Coverage   68.10%   68.14%   +0.04%     
==========================================
  Files         333      334       +1     
  Lines       51454    51528      +74     
==========================================
+ Hits        35043    35116      +73     
+ Misses      14129    14127       -2     
- Partials     2282     2285       +3     

Files Changed	Coverage Δ
runner/runner.go	69.91% <ø> (-0.13%)	⬇️
warehouse/archive/cron.go	50.00% <25.00%> (ø)
warehouse/archive/archiver.go	67.25% <66.00%> (+1.20%)	⬆️
warehouse/warehouse.go	54.53% <100.00%> (ø)

... and 18 files with indirect coverage changes

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