Colon is not allowed in column qualifiers when specifying `columns` argument

[jaeyeolshin]

Problem

Although a colon is valid character in column qualifiers, cbt command doesn't allow it.

Environment details

• Programming language:
• OS: MacOS
• Language runtime version:
• Package version: 1.22.0 72e0126 2024-08-16 17:09:27

Steps to reproduce

1. run the following cbt command

# where a is the column family and b:c is the column qualifier
$ cbt -project foo -instance bar lookup baz "qux" columns="a:b:c" 
2026/01/02 20:49:02 -creds flag unset, will use gcloud credential
2026/01/02 20:49:03 bad format for column "a:b:c"