Refactor Vector implementation

[StephenCathcart]

Closes DRIVERS-115

• Vector is now a struct that holds a slice of elements.
• Tightened constraint on VectorElement.
• Added Vector type variants to RecordValue and PropertyValue interfaces, enabling extraction via GetRecordValue and GetProperty.
• Aliases are working as intended. User-defined types are unsupported (similar to other dbtype structures).

vec := neo4j.Vector[float64]{Elems: []float64{1.0, 2.0, 3.0}}

// Create a node with a vector property
result, err := neo4j.ExecuteQuery(ctx, driver,
	"CREATE (n:VectorExample {vec: $vec}) RETURN n, n.vec AS vec",
	map[string]any{"vec": vec},
	neo4j.EagerResultTransformer)

record := result.Records[0]

// Use GetRecordValue to extract vector from record
recordVec, _, err := neo4j.GetRecordValue[neo4j.Vector[float64]](record, "vec")

// Use GetProperty to extract vector from node
node := record.Values[0].(neo4j.Node)
propVec, err := neo4j.GetProperty[neo4j.Vector[float64]](node, "vec")

[robsdedude]

Nit: could expand GetRecordValue tests to cover new types.

[robsdedude]

nit: might want to add dbtype aliases

[robsdedude]

While looking at this, I'm ever so slightly annoyed by having to read (and potentially having to write) the inner vector type twice...

I mean users can avoid this by writing a simple

func makeVec[T dbtype.VectorElement](elems []T) neo4j.Vector[T] {
	return neo4j.Vector[T]{Elems: elems}
}

or similar... As a more seasoned Go dev, what's your gut feeling? Is it worth adding such a helper function to the driver or is it unnecessary noise?