fix(tooltip): preserve raw string title and content data attributes (#43090)

[Aryan9891]

Description

Preserve raw attribute strings for data-bs-title and data-bs-content in Tooltip._getConfig() and fallback null values to empty strings in _configAfterMerge().

Motivation & Context

Fixes #43090 where passing data-bs-title="9.90" resulted in automatic normalization via JSON.parse into numeric 9.9, and data-bs-title="" was normalized to null, causing the typecheck to throw an error and break subsequent tooltip initializations.

Type of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist

• I have read the contributing guidelines
• My code follows the code style of the project
• My change introduces changes to the documentation
• I have updated the documentation accordingly
• I have added tests to cover my changes
• All new and existing tests passed

Related issues

Closes #43090