Extract db appraisal group

[TonyCTHsu]

Motivation:

From internal discussion, we want to horizontally scale our appraisal groups, instead of vertically. This means we are breaking large appraisal groups into smaller ones.

What does this PR do?

This PR extracts relational_db group from contrib group. This group includes a range of gems that are depending on a relational database.

Additional Notes

I started off with extracting activesupport group, but found there are strong coupling in our test with our db adatpers(mysql2, pg and sqlite) while activerecord does not declare dependencies for them. It would be strange to include those adapters into the activesupport group. Hence, I pivot to extract those relational database related gems. I hesitate to include other db related gems(mongodb, presto/trino, dalli) at this moment.

The original bundle exec rake test:autoinstrument is failing because the test cases were setup with a Sinatra application making db request but now the appraisal group contrib no longer contains those db gems. I consider making db request to be excessive for test case to verify the auto instrument behaviour, so I fix the task by removing the those db calls and change the dependent group to sinatra and increase the ruby version support to latest version.

[GustavoCaso]

I hesitate to include other db related gems(mongodb, presto/trino, dalli) at this moment.

Can you explain why you hesitated?

[TonyCTHsu]

I hesitate to include other db related gems(mongodb, presto/trino, dalli) at this moment.

Can you explain why you hesitated?

The reason I group those gems because they require database adapter (mysql2, pg and sqlite) to work properly. With such group, I can test the instrumentation for high level ORM (active_record, sequel and delayed_job ) and instrumentation for low level drivers (mysql2, pg and sqlite).

The ones excluded (mongodb, presto/trino, dalli) do not required those drivers or they contain their own drivers.