Correct multi-company lead visibility in portal.

[task-4482622](https://www.odoo.com/web#view_type=form&model=project.task&id=4482622)

Description of the issue/feature this PR addresses:
In a multi-company environment, portal users (partners) were unable to access Opportunities and Leads belonged to them, when these records belonged to company(branch) that is not main company. Their visibility was restricted to records from the main company, even if their access rights were configured to allow access to multiple companies.

Steps to reproduce:
1. Create a new company
2. Create a partner and grant them portal access
3. Grant the partner access right to the new company.
4. Switch to the new company and create an opportunity and assign it to
this partner (Under assigned Partner tab).
5. Log in as the partner, go to "my/opportunities."
6. The opportunity is not there.

Desired behavior after PR is merged:
Partners can see lead/opportunities from multiple companies.

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Current behavior exists for other portal endpoints such as my/subscriptions, my/sales, my/invoices but I believe that the current behavior is expected and normal for these endpoints.

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**Steps to reproduce:**

- Install the `documents_project` module.
- Create a project, set visibility to '**Invited internal users (private)**', and add Marc Demo as a follower.
- In the project settings tab, hover over the folder name and open it.
- Click the gear icon and select 'Share', ensuring Marc Demo is listed under '**People with access**'.
- Set both '**Internal Users**' and '**Anyone with the link**' to None, then click 'Done'.
- Create a task for the project and add Marc Demo as the assignee
- Upload a document via the document smart button
- Now go to the task with Marc Demo

Marc Demo cannot see the document but can see the attachment. The document smart button shows 0 count.

**Issue:**

Marc Demo, a project follower and task assignee, cannot see the document because it’s not shared with his user’s partner. 

**Solution:**

- Grant 'view' access to task assignees if project visibility is set to
  'Invited internal users (private)', allowing assignees to access the documents.
- Revoke document access for partners who are unsubscribed and no longer
  followers of the associated project and task.
- Also, implemented a test case to cover these use-cases.

opw-4702911

**Steps to reproduce:**
- Install account_budget
- Activate "Budget Management" in Accounting settings

- Go to "Accounting / Accounting / Analytic Budget"
- Create a new budget:
  * Budget Type: Expense
  * Period: [this month]
  * Budget Lines: [a line with an analytic account (AA) in 2 plans]
- Open the budget

**Issue 1:**
Create a PO at the current date with a line having only one of the AA as analytic distribution and an amount higher than the budgeted amount.
The PO line and the Budget button appear in red, but it shouldn't because the analytic distribution of the line doesn't match all the accounts defined on the budget line.
The line will not impact the budget, but it appears in red, which is confusing.

**Cause 1:**
When computing the budget lines linked to the PO line, the domain that is used is only taking into account the plans that are set on the PO line, ignoring the plans that are not set.
For the Budget button, all the PO lines are used instead of just those having the correct analytic distribution.

**Issue 2:**
- Create a PO at the current date with 2 lines:
1) a line with the same AA than the budget line and an amount higher than the budget amount
2) a line with the same AA than the budget line and an amount lower than the budget amount
- Save the PO
The first line should be red, but it is not.

**Cause 2:**
When computing the budget lines linked to the PO lines, only the last PO line has its value set.

opw-4757067