Add support of vector type to COPY command

Currently it's not possible to import rows with vector literals via COPY command.

STR:

• Create a table

  CREATE TABLE testcopyfrom (id text PRIMARY KEY, embedding_vector VECTOR<FLOAT, 6>
  

• Prepare csv file with sample data, for instance:

  1,"[0.1, 0.2, 0.3, 0.4, 0.5, 0.6]"
  2,"[-0.1, -0.2, -0.3, -0.4, -0.5, -0.6]" 

• in cqlsh run

  COPY ks.testcopyfrom FROM data.csv
  

It will result in getting:

TypeError: Received an argument of invalid type for column "embedding_vector". Expected: <class 'cassandra.cqltypes.VectorType(6)'>, Got: <class 'str'>; (required argument is not a float)