[17.0] [IMP] fieldservice_account_analytic: use python contrains instead of validation at creation for analytic lines

[rrebollo]

I found this issue after seeing the following warning:

WARNING ? odoo.api.create: The model odoo.addons.fieldservice_account_analytic.models.analytic_account is not overriding the create method in batch

When refactoring to use @api.model_create_multi, it became clear that a Python constraint is the more appropriate solution.

@BinhexTeam T18741

[OCA-git-bot]

Hi @brian10048, @osimallen, @bodedra,
some modules you are maintaining are being modified, check this out!

[rrebollo]

Failing tests are not related to this addon.