fix: serialize user-defined window functions to proto

[jcsherin]

Which issue does this PR close?

Closes #13401.

Rationale for this change

Same as #13401.

What changes are included in this PR?

1. Serializes user-defined window functions to proto

2. Adds codec methods to PhysicalExtensionCodec:

   pub trait PhysicalExtensionCodec: Debug + Send + Sync {
   
   fn try_decode_udwf(&self, name: &str, _buf: &[u8]) -> Result<Arc<WindowUDF>> {
       not_impl_err!("PhysicalExtensionCodec is not provided for window function {name}")
   }
   
   fn try_encode_udwf(&self, _node: &WindowUDF, _buf: &mut Vec<u8>) -> Result<()> {
       Ok(())
   }
   }

Are these changes tested?

Yes, roundtrip physical plan for,

1. An existing user-defined window function and,
2. A user-defined window function with a custom payload and implements PhysicalExtensionCodec.

Are there any user-facing changes?

No.

[mwylde]

Thanks! I can confirm this fixes our tests.

[jcsherin]

I just merged up from main to fix conflict.

[alamb]

Thanks again @jcsherin