cdc: improve exception message of invalid "ttl"
cdc: improve exception message of invalid "ttl"

Improve the exception message of providing invalid "ttl" value to the
table.

Previously, if you executed a CREATE TABLE query with invalid "ttl"
value, you would get a non-descriptive error message:

CREATE TABLE ks.t(pk int, PRIMARY KEY(pk)) WITH cdc = {'enabled': true, 'ttl': 'invalid'};
ServerError: stoi

This commit adds more descriptive exception messages:

CREATE TABLE ks.t(pk int, PRIMARY KEY(pk)) WITH cdc = {'enabled': true, 'ttl': 'kgjhfkjd'};
ConfigurationException: Invalid value for CDC option "ttl": kgjhfkjd

CREATE TABLE ks.t(pk int, PRIMARY KEY(pk)) WITH cdc = {'enabled': true, 'ttl': '75747885787487'};
ConfigurationException: Invalid CDC option: ttl too large

scylladb/scylla,scylladb/scylla,scylladb/scylla,scylladb/scylla