Date types simplified

[unconverged]

This pull request is mostly equal to #53 , but uses DateTime to represent DateOnly and TimeOnly columns. As a result for DuckDb's DATE columns we return a DateTime with time-related properties set to 0s and for TIME columns we return a DateTime with date-related properties set to 1s (min values for the corresponding properties).

This PR substitutes #53 , we need to choose one of them.

Fix #45

[coveralls]

Pull Request Test Coverage Report for Build 2894364867

• -8 of 93 (91.4%) changed or added relevant lines in 5 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+4.2%) to 74.789%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
DuckDB.NET.Data/Internal/PreparedStatement.cs	4	5	80.0%
DuckDB.NET.Data/DuckDBParameter.cs	3	5	60.0%
DuckDB.NET.Data/Types/DuckDBTimestamp.cs	68	70	97.14%
DuckDB.NET/DuckDBNativeObjects.cs	9	12	75.0%

Totals
Change from base Build 2890051285:	4.2%
Covered Lines:	506
Relevant Lines:	657

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💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 2895966035

• 126 of 156 (80.77%) changed or added relevant lines in 6 files are covered.
• 14 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+5.8%) to 76.437%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
DuckDB.NET.Data/Internal/PreparedStatement.cs	15	16	93.75%
DuckDB.NET.Data/Types/DuckDBTimestamp.cs	68	70	97.14%
DuckDB.NET/DuckDBNativeObjects.cs	9	12	75.0%
DuckDB.NET.Data/DuckDBDataReader.cs	11	21	52.38%
DuckDB.NET.Data/DuckDBParameter.cs	15	29	51.72%

Files with Coverage Reduction	New Missed Lines	%
DuckDB.NET.Data/DuckDBDataReader.cs	14	59.41%

Totals
Change from base Build 2890051285:	5.8%
Covered Lines:	558
Relevant Lines:	715

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💛 - Coveralls