Update mistral module compiler plugin to support generate API calls when the ai import is not present in the file

[SasinduDilshara]

Update mistral module compiler plugin to support generate API calls when the mistral import is not present in the file

Fixes: ballerina-platform/ballerina-library#8126

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 50.43%. Comparing base (cf50e26) to head (0eac95a).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #18   +/-   ##
=======================================
  Coverage   50.43%   50.43%           
=======================================
  Files           3        3           
  Lines         347      347           
  Branches      105      105           
=======================================
  Hits          175      175           
  Misses        172      172           

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