[FIX] profiler: be more pesimistic

The profiler was too optimistic. If the local variable self was not a
cursor, it assumed it was automatically an Odoo model.
Instead, only do the custom tracer methods when self is an instance of
BaseModel.

Full scenario to reproduce explained at odoo/odoo#39237

In case a method like the default_get of utm.mixing was profiled, the
tracer crashed when evaluating `__bool__(request)`.
The tracer considered self as an Odoo model while it was a werkzeug
instance with its custom __getattr__ that crashed while trying to
retrieve the content of `_name`.

Fixes odoo/odoo#39237

Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>