Generate code from SqlMetaData.xml

[paulmedynski]

Today we are reading in the SqlMetaData.xml file and parsing it into data structures at runtime. See if we can do that work at compile time and generate some static code or data structures instead to avoid runtime overhead and possible errors.

[edwardneal]

It might also be useful to account for where SqlClient stores its records of various types. At present, we've got a number of sources:

• Floating constants in TdsEnums
• MetaType
• SqlMetaDataPriv
• SqlMetaData.xml (returned via SqlConnection.GetSchema("DataTypes").)

Having a single place to add new types and to "hydrate" them with a precision/length where necessary would be convenient. In the long term, it might also help to lift some of the parsing logic out of TdsParser (although hopefully SqlClientX will pre-empt that.)