[imp] add sparse checkout

[hoangtrann]

sometimes, there can be a need to only keep certain directories after aggregate, e.g using hatch-odoo for instance and we want to install all modules included in web

this changed add a sparse-checkout attribute to keep what's specified.

./web:
    remotes:
        oca: https://github.com/OCA/web.git
    target: oca 18.0
    merges:
        - oca 18.0
    sparse-checkout:
        - web_responsive