Change .ToUpper() to .ToUpperInvariant() for culture-independent string comparisons

[Copilot]

This PR addresses culture-dependent string comparison issues by replacing all .ToUpper() calls with .ToUpperInvariant() throughout the SQLProvider codebase.

Problem

The use of .ToUpper() can cause unexpected behavior in certain locales, particularly Turkish, where the uppercase form of 'i' is 'İ' (dotted capital I) rather than 'I'. This can break SQL identifier comparisons and database schema operations when the application runs on systems with Turkish locale.

For example:

// Problematic with Turkish locale
let dataType = "int"
let isMatch = dataType.ToUpper() = "INT"  // May fail in tr-TR locale

// Culture-independent solution  
let isMatch = dataType.ToUpperInvariant() = "INT"  // Always works

Changes Made

17 instances of .ToUpper() were converted to .ToUpperInvariant() across 9 files:

Database Schema Processing

• Ssdt.DacpacParser.fs (6 changes): Data type mappings and nullability checks for SQL Server DACPAC parsing
• Providers.MsSqlServer.Ssdt.fs (2 changes): User-defined data type lookups

SQL Provider Implementations

• Providers.MsSqlServer.fs (1 change): Routine type classification (FUNCTION vs PROCEDURE)
• Providers.MsSqlServer.Dynamic.fs (1 change): Dynamic routine type classification
• Providers.MySql.fs (2 changes): Routine types and UNSIGNED column detection
• Providers.DuckDb.fs (2 changes): Provider type mappings and UNSIGNED column detection

Core Runtime

• SqlRuntime.Common.fs (1 change): Case-insensitive dummy data table lookups
• Utils.fs (1 change): SQL alias prefix generation
• SqlDesignTime.fs (1 change): Case sensitivity configuration

Benefits

✅ Culture Independence: Ensures consistent behavior across all system locales
✅ Reliability: Prevents Turkish locale issues that could break SQL operations
✅ Best Practices: Aligns with .NET guidelines for internal string processing
✅ Backward Compatibility: No breaking changes to public APIs

Testing

Created comprehensive test suite verifying:

• Database type mapping scenarios
• SQL routine type classifications
• Column type detection (UNSIGNED checks)
• Culture independence (Turkish vs English locale)
• All string comparison patterns used in the codebase

The changes ensure robust, predictable behavior for SQL schema operations regardless of the user's system locale settings.

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