feat(dashboard): add threshold series overrides support

[Aashirwadjain]

Description

This PR aims to add support for threshold series overrides in widget billboard.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.73%. Comparing base (6070563) to head (9db1272).

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #1335       +/-   ##
===========================================
+ Coverage   36.20%   70.73%   +34.52%     
===========================================
  Files         135      135               
  Lines        6192     6192               
===========================================
+ Hits         2242     4380     +2138     
+ Misses       3751     1422     -2329     
- Partials      199      390      +191     

Flag	Coverage Δ
integration	59.73% <ø> (?)
unit	36.20% <ø> (ø)

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