In this commit, we add a new `Zero` method for the `RecordT` type. This
method allows a caller to create the zero record for a type without
needing to reference the actual TLV type.
With this we go from this:
```go
sig1 := tlv.ZeroRecordT[tlv.TlvType1, Sig]()
```
To this:
```
sig1 := c.CloserNoClosee.Zero()
```