Fix let expression usage inside query actions

[LakshanWeerasinghe]

Purpose

$subject

Fixes #40229

Approach

In the query desugar we were desugaring the expression of the let expression before desugaring the let variable declaration. Because of that there were unwanted statements added at the query desugar level resulted in compiler crash. Changing the desuaging order will fixed the issue.

Check List

• Read the Contributing Guide
• Updated Change Log
• Checked Tooling Support (#)
• Added necessary tests
  • Unit Tests
  • Spec Conformance Tests
  • Integration Tests
  • Ballerina By Example Tests
• Increased Test Coverage
• Added necessary documentation
  • API documentation
  • Module documentation in Module.md files
  • Ballerina By Examples

[codecov]

Codecov Report

Attention: 522 lines in your changes are missing coverage. Please review.

Comparison is base (04b5210) 76.68% compared to head (7ecb277) 76.67%.
Report is 787 commits behind head on master.

Files	Patch %	Lines
...rc/main/java/io/ballerina/cli/cmd/ToolCommand.java	0.00%	78 Missing ⚠️
...2/ballerinalang/compiler/bir/model/BIRVisitor.java	0.00%	70 Missing ⚠️
...java/io/ballerina/runtime/internal/ValueUtils.java	38.57%	42 Missing and 1 partial ⚠️
...ballerinalang/central/client/CentralAPIClient.java	25.53%	29 Missing and 6 partials ⚠️
...in/java/io/ballerina/projects/DependencyGraph.java	0.00%	24 Missing ⚠️
...o/ballerina/projects/internal/ManifestBuilder.java	76.92%	16 Missing and 8 partials ⚠️
...rc/main/java/io/ballerina/cli/cmd/PushCommand.java	60.00%	14 Missing and 2 partials ⚠️
...lerina/cli/task/RunBallerinaPreBuildToolsTask.java	65.95%	10 Missing and 6 partials ⚠️
...rinalang/compiler/bir/emit/InstructionEmitter.java	0.00%	15 Missing ⚠️
...a/io/ballerina/cli/launcher/util/BalToolsUtil.java	0.00%	14 Missing ⚠️
... and 44 more

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #42068      +/-   ##
============================================
- Coverage     76.68%   76.67%   -0.01%     
- Complexity    53019    53020       +1     
============================================
  Files          2883     2883              
  Lines        199924   199924              
  Branches      26024    26024              
============================================
- Hits         153305   153301       -4     
- Misses        38157    38160       +3     
- Partials       8462     8463       +1     

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