Replace CSV examples into TEXT examples in docs

To guide users to move from CSV into TEXT storage type, this issue propose to replace CSV examples into TEXT examples.

• Case 1: An example with no delimiter definition

  - USING CSV
  + USING TEXT WITH ('textfile.delimiter'=',')
  

• Case 2: An example with text delimiter definition

  - USING CSV WITH('text.delimiter'='\u0001',...)
  + USING TEXT WITH('text.delimiter'='\u0001',...)