Add sqlalchemy test matrix to ensure compatibility with 1.3 version

[mdesmet]

Fixes #250

Description

scalar_one() and scalar_one_or_none() are not available in sqlalchemy 1.3. They have been replaced by scalar() calls.

sqlalchemy has also been added into the ci matrix to ensure compatibility with 1.3 and 1.4 versions.

Non-technical explanation

Release notes

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* Use sqlalchemy 1.3 compatible methods in sqlalchemy dialect.

[hovaesco]

Let's create a compatibility section under https://github.com/trinodb/trino-python-client#sqlalchemy and document which SQLAlchemy versions are supported.

[mdesmet]

Let's create a compatibility section under https://github.com/trinodb/trino-python-client#sqlalchemy and document which SQLAlchemy versions are supported.

Let's handle this as follow up.

[mdesmet]

@hashhar, @hovaesco: My point is that both 1.3 and 1.4 are supported but there will be some rough edges which will only surfaced by adding more integration tests.

I have added the compatibility section though.

[john-bodley]

@mdesmet what's wrong with simply adding a dependency constraint that only SQLAlchemy >= 1.4 is supported? This adheres to the KISS principle and doesn't pollute the code, unit tests, CI build matrix etc.

[hashhar]

Because we can't control what other third party tools use as the version of SQLAlchemy.

I'd love to be able to force a version of SQLAlchemy on the consumer to simply our lives but it's not possible today.