Fixes the way record end hours are computed in calendar views.
Before this commit: objects `record start` and `record end` properties being copied by reference
and being incorrectly rewritten by other functions.
This caused incorrect end hour computations (and a SQL crash in the Planning app).
Now, objects are copied by value and don't interfere with each other.
Task 2072961
closesodoo/odoo#37690
Signed-off-by: Aaron Bohy (aab) <aab@odoo.com>