chore(docs): add basic samples for async data client

[daniel-sanche]

This PR adds

• samples for the new async data client to match the samples in the Write examples and Read examples sections of the public docs.
  • All samples are as similar as possible to existing ones, with the addition of *_async_* to the region tag
• a new async version of the hello world sample

Currently missing are the samples on the Use filters and Deletes pages. Let me know if you want me to add those as well

[snippet-bot]

Here is the summary of changes.

You are about to add 20 region tags.

• samples/hello/async_main.py:30, tag bigtable_async_hw_imports
• samples/hello/async_main.py:41, tag bigtable_async_hw_connect
• samples/hello/async_main.py:46, tag bigtable_async_hw_create_table
• samples/hello/async_main.py:68, tag bigtable_async_hw_write_rows
• samples/hello/async_main.py:92, tag bigtable_async_hw_create_filter
• samples/hello/async_main.py:98, tag bigtable_async_hw_get_with_filter
• samples/hello/async_main.py:99, tag bigtable_async_hw_get_by_key
• samples/hello/async_main.py:109, tag bigtable_async_hw_scan_with_filter
• samples/hello/async_main.py:110, tag bigtable_async_hw_scan_all
• samples/hello/async_main.py:119, tag bigtable_async_hw_delete_table
• samples/snippets/data_client/data_client_snippets_async.py:18, tag bigtable_async_write_simple
• samples/snippets/data_client/data_client_snippets_async.py:41, tag bigtable_async_writes_batch
• samples/snippets/data_client/data_client_snippets_async.py:68, tag bigtable_async_write_increment
• samples/snippets/data_client/data_client_snippets_async.py:92, tag bigtable_async_writes_conditional
• samples/snippets/data_client/data_client_snippets_async.py:125, tag bigtable_async_reads_row
• samples/snippets/data_client/data_client_snippets_async.py:139, tag bigtable_async_reads_row_partial
• samples/snippets/data_client/data_client_snippets_async.py:156, tag bigtable_async_reads_rows
• samples/snippets/data_client/data_client_snippets_async.py:176, tag bigtable_async_reads_row_range
• samples/snippets/data_client/data_client_snippets_async.py:198, tag bigtable_async_reads_prefix
• samples/snippets/data_client/data_client_snippets_async.py:219, tag bigtable_async_reads_filter

---

This comment is generated by snippet-bot.
If you find problems with this result, please file an issue at:
https://github.com/googleapis/repo-automation-bots/issues.
To update this comment, add snippet-bot:force-run label or use the checkbox below:

• Refresh this comment

[mutianf]

should we add a comment here saying the default is 100 and is good for most use cases, setting it to 2 just for the example purpose?
Or we don't change the defaults here, and just manually flush in the end. And I would also add some comments on why manual flush is needed, something like "flush will be called automatically when a batch is full, the default batch size is 100".

[daniel-sanche]

Ok, maybe I'll remove the arguments here if that's confusing. A manual flush isn't needed since we are using a async with statement, it will flush and close everything for us at the end of this block

Let me know if you think any extra comments are needed to clarify anything

[mutianf]

do we need to flush?

[daniel-sanche]

No, we're using a context manager (async with), so it will automatically call close for us at the end of the block