Fix issues in toXml API and update the docs

[kalaiyarasiganeshalingam]

Purpose

$Subject

Fixes ballerina-platform/ballerina-library#3713
ballerina-platform/ballerina-library#3716

Examples

Checklist

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

[codecov]

Codecov Report

Base: 88.24% // Head: 88.86% // Increases project coverage by +0.61% 🎉

Coverage data is based on head (0ede599) compared to base (5b05c84).
Patch coverage: 89.47% of modified lines in pull request are covered.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #470      +/-   ##
============================================
+ Coverage     88.24%   88.86%   +0.61%     
- Complexity      215      220       +5     
============================================
  Files             8        8              
  Lines           817      835      +18     
  Branches        284      282       -2     
============================================
+ Hits            721      742      +21     
+ Misses           56       54       -2     
+ Partials         40       39       -1     

Impacted Files	Coverage Δ
...a/io/ballerina/stdlib/xmldata/utils/Constants.java	100.00% <ø> (ø)
...o/ballerina/stdlib/xmldata/utils/XmlDataUtils.java	95.69% <89.18%> (+1.65%)	⬆️
ballerina/xmldata.bal	96.89% <100.00%> (+0.53%)	⬆️
...in/java/io/ballerina/stdlib/xmldata/XmlToJson.java	82.58% <0.00%> (-0.05%)	⬇️
...n/java/io/ballerina/stdlib/xmldata/MapFromXml.java	86.88% <0.00%> (ø)

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[github-actions]

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[github-actions]

Closed PR due to inactivity for more than 18 days.