importccl: add the missing tests for unsupported mysql types

[knz]

The code to handle types in mysqlColToCockroach (read_import_mysql.go) has several error conditions that do not have unit tests yet.

The test should verify that CockroachDB indeed reports errors for unsupported column types, and that these errors are accompanied by suitable telemetry.

cc @rolandcrosby.

Jira issue: CRDB-4725

[github-actions]

We have marked this issue as stale because it has been inactive for
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or adding a comment will keep it active. Otherwise, we'll close it in
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[fqazi]

Import is now owned by queries, so moving this over.