Add support for claim-wise uniqueness validation

[AfraHussaindeen]

Purpose

Introduce first-class support for attribute uniqueness validation.

Changes to the UI:

A new dropdown will be added to the attribute configuration section under the General tab, giving administrators the flexibility to define the scope of uniqueness validation for each attribute. The dropdown will offer three options:

• None: No uniqueness validation.
• Within Userstore: Validation applies only within the selected user store.
• Across Userstores: Validation is enforced across all user stores.

Note : This dropdown will be displayed only when the uniqueness validation feature is enabled via the deployment.toml

[identity_mgt.user_claim_update.uniqueness]
enable = true

Related Issues

• UI Improvement for Attribute Uniqueness Configuration product-is#21507

To be merged after

• Add support for claim-wise uniqueness validation carbon-identity-framework#6113

Checklist

• e2e cypress tests locally verified. (for internal contributers)
• Manual test round performed and verified.
• UX/UI review done on the final implementation.
• Documentation provided. (Add links if there are any)
• Relevant backend changes deployed and verified
• Unit tests provided. (Add links if there are any)
• Integration tests provided. (Add links if there are any)

Security checks

• Followed secure coding standards in http://wso2.com/technical-reports/wso2-secure-engineering-guidelines
• Ran FindSecurityBugs plugin and verified report
• Confirmed that this PR doesn't commit any keys, passwords, tokens, usernames, or other secrets

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 32.02%. Comparing base (f9090c4) to head (07df2e4).
Report is 161 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7106      +/-   ##
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+ Coverage   31.79%   32.02%   +0.22%     
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  Files          41       41              
  Lines         890      893       +3     
  Branches      220      220              
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+ Hits          283      286       +3     
+ Misses        607      557      -50     
- Partials        0       50      +50     

Flag	Coverage Δ
@wso2is/core	32.02% <ø> (+0.22%)	⬆️

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[wso2-jenkins-bot]

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