Add query-expr clause to handle duplicate table keys

[lasinicl]

Purpose

$title

Fixes #22641

Approach

Add on conflict clause to query expression.

Samples

            from var person in personList
            select {
                   firstName: person.firstName,
                   lastName: person.lastName,
                   age: person.age
            }
            on conflict error("PersonNotFound");

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-io]

Codecov Report

Merging #22983 into new-table-impl will not change coverage.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           new-table-impl   #22983   +/-   ##
===============================================
  Coverage           14.59%   14.59%           
===============================================
  Files                  51       51           
  Lines                1411     1411           
  Branches              219      219           
===============================================
  Hits                  206      206           
  Misses               1189     1189           
  Partials               16       16           

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[CLAassistant]

All committers have signed the CLA.

[grainier]

Better to use a proper example. This shouldn't be allowed and type checker should only allow following [1];

join-on-condition := "on" expression "equals" expression

[1] ballerina-platform/ballerina-spec#435

[grainier]

Same as previous; better to use a proper example.

[grainier]

merged in : grainier#29