Go-Ora improvements

[stle04]

• Regexp variables lazy initialization
• fix unit tests
• fix ConvertIntervalYM_DTY with wrong unsigned integer usage
• code formatting(gofumpt for one code style)

[kopaygorodsky]

Hey, I've stumbled upon this PR due to an error I'm facing now.
So I have my custom type

type UUID []byte

// Value implements sql.Valuer so that UUIDs can be written to databases
// transparently. This method returns a byte slice representation of uuid
func (u UUID) Value() (driver.Value, error) {
	return []byte(u), nil
}

Column type is RAW(16), I'm trying to execute INSERT INTO and one of my params is ID of type I mentioned above.
Execution fails with this error parameter require array value which I checked is wrong in this case as my value is in fact an "array".

[kopaygorodsky]

oh, nvm, I'm wrong about this particular PR, the issue is not related to this one.