Rename data_sets argument and _data_sets attribute of DataCatalog

[deepyaman]

Description

In the DataCatalog rename the data_sets argument to datasets and the _data_sets attribute to _datasets.

To do

• Should we first deprecate the old one naming? -> Discussed in grooming, deprecation warnings seems like a lot of effort for something that's probably not used by a lot of people. We will mention this very clearly in the migration notes. The _data_sets attribute is mentioned in docs: https://docs.kedro.org/en/stable/data/how_to_create_a_custom_dataset.html#thread-safety
• Also renamedef data_sets() in Pipeline.
• and rename all other usages of data_sets in the codebase. E.g. variable and argument names + docs.

[astrojuanlu]

@noklam I recall you made a comment somewhere about dataset access from the catalog, but I can't locate it

[noklam]

Maybe this?

• Clean up catalog.datasets and catalog._data_sets #2999

[MinuraPunchihewa]

Hello Kedro Team,
I would like to start contributing to the project and I thought this might be a good place to start. Can I take this up or if you have any other suggestions for a new contributor, I would love to hear it.

[astrojuanlu]

Hey @MinuraPunchihewa , please go ahead! 🚀 Make sure to read our CONTRIBUTING.md and if you need any help, let us know, here or in https://slack.kedro.org

[MinuraPunchihewa]

Thanks, @astrojuanlu!

[astrojuanlu]

Should this change happen in main or develop?

[merelcht]

Should this change happen in main or develop?

develop because it's a breaking change.

[merelcht]

Completed in #3115