ColumnType methods panic when unsupported

[kellymtrinh]

Describe the bug

When using this driver with the go sql package, ColumnType.DatabaseTypeName, ScanType, Length, and DecimalSize panics when a column type is unsupported.

Could this return the nil values as appropriate when it's not supported, to match what is described here: "If an empty string is returned, then the driver type name is not supported."?

Current behavior means calling ColumnTypes() or related methods in the database/sql lib panics if I'm doing something like select * on a table with an unsupported column (or trying to use the driver for generic queries). Matching the spec would let clients handle the cases.

To Reproduce

func TestMakeGoLangUnsupportedType(t *testing.T) {
	makeGoLangTypeName(typeInfo{TypeId: 123})

}
// --- FAIL: TestMakeGoLangTypeName1 (0.00s)
// panic: not implemented makeGoLangTypeName for type 123 [recovered]
// 	panic: not implemented makeGoLangTypeName for type 123

Expected behavior
Instead of a panic, it should return nil values as appropriate for callers to handle.

Further technical details

The panic happens in makeGoLangTypeName, which is used in ColumnTypeScanType and ColumnTypeScanType.
The other methods can be found in types.go too.