Update cache configurations to allow null in the default setting

[SasinduDilshara]

Update cache configurations to allow null in the default setting

Fixes wso2/product-ballerina-integrator#1783

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.77%. Comparing base (2e43a99) to head (f6e9db1).
⚠️ Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #3      +/-   ##
==========================================
+ Coverage   85.16%   85.77%   +0.60%     
==========================================
  Files           2        2              
  Lines         236      239       +3     
  Branches       81       82       +1     
==========================================
+ Hits          201      205       +4     
+ Misses         35       34       -1     

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