chore: populate context with validation errors when context is nil

[Jayachand]

Description

enrich tracking plan validation errors when context is nil or not present

Linear Ticket

https://linear.app/rudderstack/issue/DAT-312/handle-scenarios-where-context-is-undefined-or-is-not-present-in-the

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: 100.00% and project coverage change: -0.03% ⚠️

Comparison is base (fdfb4f6) 69.06% compared to head (2e49a95) 69.04%.
Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3815      +/-   ##
==========================================
- Coverage   69.06%   69.04%   -0.03%     
==========================================
  Files         349      349              
  Lines       51899    51909      +10     
==========================================
- Hits        35845    35841       -4     
- Misses      13748    13764      +16     
+ Partials     2306     2304       -2     

Files Changed	Coverage Δ
processor/trackingplan.go	57.03% <100.00%> (+3.64%)	⬆️

... and 8 files with indirect coverage changes

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