Add interface to get results in standard formats from run_raw_sql

[jlaneve]

Please describe the feature you'd like to see

When I use aql.run_raw_sql, I find myself writing handlers like:

@aql.run_raw_sql(..., handler = lambda x: x.fetchall())

@aql.run_raw_sql(..., handler = pd.DataFrame(x.fetchall(), columns = x.keys()))

It seems like there are a few natural results formats (list, dataframe) that you'd want to get results in, but the user is responsible for making these handlers. Additionally, I can't just use the same handler for both SELECT and CREATE TABLE functions because sqlalchemy's ResultProxy errors if there are no results and you call x.fetchall()

Describe the solution you'd like
Add two fields to the decorator/operator:

• results_format: let the user specify a common format they want their results (list, dataframe)
• fail_on_empty: let the user decide what the behavior should be if there are no results

Are there any alternatives to this feature?

We could also consider exporting common handlers instead of forcing the user to define them.

Additional context
Add any other context about the feature request here.

I'm considering this from the perspective of the Astro Cloud IDE, in which our requirements are:

• get the results as a DataFrame
• use the same decorator/code for all run_raw_sql's, regardless of wether it's a SELECT or INSERT
  • this is because we're generating a DAG and parsing the SQL code to do this dynamically is unreliable

Acceptance Criteria

• All checks and tests in the CI should pass
• Unit tests (90% code coverage or more, once available)
• Integration tests (if the feature relates to a new database or external service)
• Example DAG
• Docstrings in reStructuredText for each of methods, classes, functions and module-level attributes (including Example DAG on how it should be used)
• Exception handling in case of errors
• Logging (are we exposing useful information to the user? e.g. source and destination)
• Improve the documentation (README, Sphinx, and any other relevant)
• How to use Guide for the feature (example)

[utkarsharma2]

We need to update/add documentation for these new params. Will take care in a separate PR.