Update YAML module APIs as isolated and update variable name

[madhukaw]

Purpose

Fixes ballerina-platform/ballerina-library#4439

Examples

Checklist

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

[codecov]

Codecov Report

Patch coverage: 95.00% and project coverage change: -0.01 ⚠️

Comparison is base (2141d0e) 94.14% compared to head (5f316a0) 94.14%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main       #7      +/-   ##
==========================================
- Coverage   94.14%   94.14%   -0.01%     
==========================================
  Files          44       44              
  Lines        2170     2169       -1     
  Branches     1356     1356              
==========================================
- Hits         2043     2042       -1     
  Misses        127      127              

Impacted Files	Coverage Δ
ballerina/modules/composer/collection.bal	92.30% <ø> (ø)
ballerina/modules/composer/scalar.bal	94.91% <ø> (ø)
ballerina/modules/composer/state.bal	100.00% <ø> (ø)
ballerina/modules/emitter/mapping.bal	100.00% <ø> (ø)
ballerina/modules/emitter/sequence.bal	100.00% <ø> (ø)
ballerina/modules/lexer/context.bal	93.15% <ø> (ø)
ballerina/modules/lexer/error.bal	100.00% <ø> (ø)
ballerina/modules/lexer/lexer.bal	86.84% <ø> (ø)
ballerina/modules/parser/data.bal	90.65% <ø> (ø)
ballerina/modules/parser/directive.bal	100.00% <ø> (ø)
... and 26 more

☔ View full report in Codecov by Sentry.
📢 Do you have feedback about the report comment? Let us know in this issue.