changes in operation to match with the figma design & flow

[Ishankoradia]

• Add default value option to coalesce operation. Constant value being used needs to be properly quoted.
• Add support for replace operation. This is basically updating/replacing values in a column.
  • REPLACE operation in both warehouses only works for strings/text
  • Test for postgres
  • Test for bigquery
  • Test in merge operation chaining

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 77.04918% with 14 lines in your changes are missing coverage. Please review.

Project coverage is 80.70%. Comparing base (897a878) to head (a29b9c6).

Files	Patch %	Lines
dbt_automation/operations/replace.py	75.00%	10 Missing ⚠️
dbt_automation/operations/coalescecolumns.py	75.00%	3 Missing ⚠️
dbt_automation/utils/columnutils.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #77      +/-   ##
==========================================
- Coverage   80.84%   80.70%   -0.15%     
==========================================
  Files          22       23       +1     
  Lines         966     1026      +60     
==========================================
+ Hits          781      828      +47     
- Misses        185      198      +13     

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