Add isort (for sorting imports)

[mdesmet]

Introduces isort (sorting imports)

• Added isort as "test" dependencies
• Run pre-commit run --all-files to standardize formatting and import sorting.

[mdesmet]

Some flakyness in the tests, might be related to not having merged #220 but not totally sure.

[hashhar]

@mdesmet See also https://github.com/trinodb/trino-python-client/commit/cffd2b232d9298321c34430f0ac829f6b6ebea8f#r83714277 - not sure if that's the cause.

[mdesmet]

@hashhar: As discussed I have removed black from this PR and only kept isort. PTAL

[mdesmet]

@hashhar: PTAL