Fix resolver returning null when record has service objects or map of service objects as its field

[MohamedSabthar]

Purpose

Fixes: #3466
Fixes: #3579

Examples

Checklist

• Linked to an issue
• Updated the changelog
• Added tests
• Updated the spec
• Checked native-image compatibility

[codecov]

Codecov Report

Base: 86.75% // Head: 86.78% // Increases project coverage by +0.02% 🎉

Coverage data is based on head (fbb3ab4) compared to base (2bf672b).
Patch coverage: 100.00% of modified lines in pull request are covered.

❗ Current head fbb3ab4 differs from pull request most recent head ed496e9. Consider uploading reports for the commit ed496e9 to get more accurate results

Additional details and impacted files

@@             Coverage Diff              @@
##           2201.2.x    #1029      +/-   ##
============================================
+ Coverage     86.75%   86.78%   +0.02%     
============================================
  Files            60       60              
  Lines          4531     4533       +2     
  Branches       2497     2496       -1     
============================================
+ Hits           3931     3934       +3     
  Misses          557      557              
+ Partials         43       42       -1     

Impacted Files	Coverage Δ
ballerina/engine_utils.bal	96.42% <100.00%> (ø)
ballerina/response_generator.bal	95.23% <100.00%> (+0.07%)	⬆️
...allerina/stdlib/graphql/runtime/engine/Engine.java	79.36% <0.00%> (+0.79%)	⬆️

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[ThisaruGuruge]

How does this handle the subscription scenarios? SInce the subscriptions are handled through a separate flor in 2201.2.x branch, we have to fix that.

[MohamedSabthar]

How does this handle the subscription scenarios? SInce the subscriptions are handled through a separate flor in 2201.2.x branch, we have to fix that.

Yes I noticed subscription is handled in java level and this bug is not present in java implementation. I'll update the PR with test cases for subscription