Feat(dlt): Add support to override the dlt pipelines directory

[themisvaltinos]

This update adds support to provide an explicit folder for the dlt pipelines. The default location for the pipelines folders is in the user's home directory: ~/.dlt/pipelines/<pipeline_name>, but in cases where you use a different directory, this allows to provide a specific one using the dlt-path argument for the sqlmesh init command:

$ sqlmesh init -t dlt --dlt-pipeline <pipeline-name> --dlt-path <pipelines_directory> dialect

as well as the sqlmesh dlt_refresh command:

$ sqlmesh dlt_refresh <pipeline-name> --dlt-path <pipelines_directory>

DLT reference: https://dlthub.com/docs/general-usage/pipeline#separate-working-environments-with-pipelines_dir

Slack thread: https://tobiko-data.slack.com/archives/C044BRE5W4S/p1741767926216659