In the current code, for each slot, and for each "available"
resource, we check if the resource is available on the slot,
based on availability values. Then, we check the remaining
capacity of that resource. Also, linked resources information
is added when computing the original resource remaining capacity.
If many linked resources exist, this will be done several times
and is not useful.

This commit makes that loop disappear. We now check all resources
at once in terms of availability, and linked resources that could
be selected (in the appointment resources, in the slot resources
(if any restricted resource)) at the same time. Then, the total
capacity is the sum of the resource remaining capacity and the
ones of available linked resources.

Therefore, _slot_availability_is_resource_available is renamed to
_slot_available_resources, as it now takes more than one resource
and returns all resources among 'resources' that are valid on
the slot, based on the availability_values, slot restrictions and
booking lines.

A noticeable difference is mainly seen when using many resources
(and linked resources). For instance, a restaurant with a lot of
small tables will have their slot availability check much shorter.

BENCHMARK, LOCAL (time only, as number of requests does not change)
Only appointment installed

For a restaurant with
- 10 tables of 2
- 5 tables of 2 linked, 2 times
- 10 tables of 4
- 2 table of 2
- time then auto assign

On loading /appointment/id:
~ 3.1s -> ~ 1.6s
On selecting any number of people (1 to 10):
[2s, 2.5s] -> [0.6s, 0.8s]

Task-4144524

**Issue**
Having supplier pricelists with at least one vendor inaccessible to the current user can trigger an access error when creating an RFQ approval request.

**Steps to reproduce**
- Have two companies A and B and two users u1 and u2
- user u2 only have access to company A
- With user u1:
	- Create two vendors v1 and v2 without any company assigned
	- Create vendor pricelists for a product for each vendor and assign the company A to the pricelist
- Add the company B for the vendor v2
- With user u2:
	- Open approval application
	- Try to create an approval for an RFQ for that product (the vendor v1 will be automatically selected)
	- Save it -> An access error is thrown

**Cause**
Saving the approval request computes `has_no_seller`, which calls `_select_seller`: https://github.com/odoo/enterprise/blob/03c737685ff6dfc95a8bc72491646774fc426b1f/approvals_purchase/views/approval_product_line_views.xml#L9 https://github.com/odoo/enterprise/blob/03c737685ff6dfc95a8bc72491646774fc426b1f/approvals_purchase/models/approval_product_line.py#L32 https://github.com/odoo/enterprise/blob/03c737685ff6dfc95a8bc72491646774fc426b1f/approvals_purchase/models/approval_product_line.py#L62-L70 
Which filtered the right seller
https://github.com/odoo/odoo/blob/c37e76850d3ff790b76493bd1003d80e170bd4bf/addons/product/models/product_product.py#L759 
By preparing the sellers:
https://github.com/odoo/odoo/blob/c37e76850d3ff790b76493bd1003d80e170bd4bf/addons/product/models/product_product.py#L721 https://github.com/odoo/odoo/blob/c37e76850d3ff790b76493bd1003d80e170bd4bf/addons/product/models/product_product.py#L712 
Please note that `self.seller_ids` contains both sellers (even v2) By filtering the suppliers:
https://github.com/odoo/odoo/blob/c37e76850d3ff790b76493bd1003d80e170bd4bf/addons/product/models/product_supplierinfo.py#L104-L105 
But at that point, one of the supplier in `self`, can be accessed, thus an access error is thrown while trying to access its associated `partner_id`.

opw-6203910

Forward-Port-Of: odoo/enterprise#120251

### Issue
Loading a large General Ledger (e.g., during an "Unfold All" action)
and retrieving display names for thousands of journal lines 
(`account.move.line`) causes excessive memory and performance overhead.

Profiling with `memray` showed that one of the main memory hotspots 
was located in `custom_label_builder`.

**Previous behavior:** Accessing `record.display_name` in a loop without
an explicit `fetch()` call triggered lazy computation of the field via
`_compute_display_name()`. When the compute method accessed stored
dependency fields (such as `name`, `ref`, `move_id`), each cache miss
went through `_fetch_field()`, which greedily loaded **all fields sharing
the same prefetch group** on the model, far beyond the dependencies of
`display_name` alone. This caused the ORM cache to be filled with many
unnecessary stored fields for every record in the prefetch set.

---

### Dataset Volume
The performance metrics were captured using a dataset consisting of:
* **455,694** Journal Items (`account.move.line`)
* **19,947** Journal Entries (`account.move`)

---

### Solution
Add a single `fetch(['display_name'])` call on the browsed recordset.
By calling `fetch(['display_name'])` upfront, the ORM goes through 
`_determine_fields_to_fetch(['display_name'])`, which walks
only the declared `field_depends` of `display_name` and fetches **only
those specific stored fields**. nothing more.

---

### Impact & Results

| Metric | Before Optimization | After Optimization | Change / Note |
| :--- | :--- | :--- | :--- |
| **Peak Memory** | ~856 MB | ~223 MB | ~74% reduction |
| **Execution Time** | 2.48s | 2.13s | About the same time with multiple tries |

OPW-6275158