Introduce provider-agnostic DataAccessDbType/DataAccessParameterDirection and map in AddParameter helpers

[habbs19]

Motivation

• Remove direct provider enum dependencies from consumer code by introducing a single, provider-agnostic parameter type enum.
• Provide a consistent parameter direction enum so callers do not need to reference provider-specific ParameterDirection types.
• Allow AddParameter helpers to accept core enums and map them to provider-specific types internally to reduce cross-project references.
• Keep existing provider behavior by mapping core enums to each provider's native types.

Description

• Add DataAccessDbType and DataAccessParameterDirection enums in DataAccessProvider.Core/Types to represent parameter type and direction respectively.
• Update AddParameter extension methods for MSSQL, MySQL, Postgres, Oracle and Snowflake to accept DataAccessDbType and DataAccessParameterDirection and map them to provider-specific types via MapDbType/MapDirection helpers.
• Update demo code, README examples and unit test sources to use DataAccessDbType in parameter calls (e.g., AddParameter(..., DataAccessDbType.String, ...)).
• Preserve previous overloads' behavior by translating to the same provider types internally, and throw ArgumentOutOfRangeException for unsupported mappings.

Testing

• No automated tests were executed as part of this change.
• Unit test source files were updated to reference DataAccessDbType, but test runs were not performed here.
• No CI or build verification was performed by this patch.
• Consumers should run dotnet build and dotnet test in their environment to validate compilation and behavior.

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Codex Task