Make code samples conform to rubric

[skuruppu]

Spanner code samples should conform to the rubric.

[skuruppu]

For the record, the samples with the following region tags still need the command line tool support as they appear in the getting started guide:

• spanner_create_database
• spanner_quickstart
• spanner_dml_getting_started_insert
• spanner_insert_data
• spanner_query_data
• spanner_query_with_parameter
• spanner_read_data
• spanner_add_column
• spanner_update_data
• spanner_query_data_with_new_column
• spanner_dml_getting_started_update
• spanner_create_index
• spanner_read_data_with_index
• spanner_create_storing_index
• spanner_read_data_with_storing_index
• spanner_read_only_transaction

[skuruppu]

@asthamohta just for reference, I have internal changes pending submission to update the following samples to point to the new samples created in #1347:

• spanner_query_data_with_index
• spanner_read_data_with_storing_index
• spanner_read_data_with_index

Even after these changes are submitted, you may not be able to delete the old version of the sample if it's still used in the Node.js getting started guide as per https://github.com/googleapis/nodejs-spanner/issues/1295#issuecomment-802580341.

Before deleting old samples, you also need to make sure that translated docs pages are picking up the new link to the sample.

[asthamohta]

Got it. Thanks Shanika