chore: stat for reporting badger db size

[vamsikrishnakandi]

Description

Added new stat for reporting badger db size

Linear Ticket

Part of OBS-754

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

Attention: Patch coverage is 30.76923% with 9 lines in your changes missing coverage. Please review.

Project coverage is 74.83%. Comparing base (f182738) to head (1069166).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...se/reporting/event_sampler/badger_event_sampler.go	30.00%	7 Missing ⚠️
...erprise/reporting/event_sampler/stats_collector.go	33.33%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5423      +/-   ##
==========================================
+ Coverage   74.80%   74.83%   +0.02%     
==========================================
  Files         440      440              
  Lines       61635    61648      +13     
==========================================
+ Hits        46107    46134      +27     
+ Misses      12988    12969      -19     
- Partials     2540     2545       +5     

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