[YCQL] Review & fix help pages in ycqlsh tool

[OlegLoginov]

Jira Link: DB-9119

Description

1. Review the tool help:

ycqlsh> help

Documented shell commands:
===========================
CAPTURE  CLS          COPY  DESCRIBE  EXPAND  LOGIN   SERIAL  SOURCE  TRACING
CLEAR    CONSISTENCY  DESC  EXIT      HELP    PAGING  SHOW    TIMING  UNICODE

CQL help topics:
================
AGGREGATES               CREATE_KEYSPACE           DROP_TRIGGER      TEXT     
ALTER_KEYSPACE           CREATE_MATERIALIZED_VIEW  DROP_TYPE         TIME     
ALTER_MATERIALIZED_VIEW  CREATE_ROLE               DROP_USER         TIMESTAMP
...

2. Fix help links.
   For example: ycqlsh> help list_roles opens file:///usr/share/doc/cassandra/CQL.html#listRolesStmt.
   I think it should open YB help pages.

Issue Type

kind/bug

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