[FIX] account: deadlock on install

- When installing an accounting l10n module, the method `try_loading_for_current_company`
  is called and could cause a deadlock.
  The deadlock is caused by the fact that if the installation is started
  via a web request the code tries to retrieve the current user's
  company by doing `request.env.user.company_id`.

  This causes issues since the installation code has its own postgresql
  cursor while calling `request.env.user.company_id` will create its own
  cursor.

  So two cursors exists for the same Odoo worker.
  The installation cursor asks for a lock on `res_users` while the
  second cursor (the request one) will try to read on `res_users` and
  wait the first lock to be dropped.

  The lock is never dropped since the python code isn't running anymore
  waiting for the `request.env.user.company_id` to be completed.
  Causing the deadlock.

  To fix the issue, we avoid the creation/usage of a cursor created by
  `requesŧ`.
  So to retrieve the current user's company, we read the user id on the
  request's session, then browse the `res.user` record with the
  installation cusror.

  Fix issue introduced by commit d40956c790

closes odoo/odoo#29927

addons/account/models/chart_template.py

@@ -165,9 +165,10 @@ class AccountChartTemplate(models.Model):
         of accounts had been created for it yet.
         """
         self.ensure_one()
-        if request and request.db:
-            company_id = request.env.user.company_id.id
-            company = self.env['res.company'].browse(company_id)
+        # do not use `request.env` here, it can cause deadlocks
+        if request and request.session.uid:
+            current_user = self.env['res.users'].browse(request.uid)
+            company = current_user.company_id
         else:
             # fallback to company of current user, most likely __system__
             # (won't work well for multi-company)
@@ -185,9 +186,10 @@ class AccountChartTemplate(models.Model):
         rights.
         """
         self.ensure_one()
-        if request and request.db:
-            company_id = request.env.user.company_id.id
-            company = self.env['res.company'].browse(company_id)
+        # do not use `request.env` here, it can cause deadlocks
+        if request and request.session.uid:
+            current_user = self.env['res.users'].browse(request.uid)
+            company = current_user.company_id
         else:
             # fallback to company of current user, most likely __system__
             # (won't work well for multi-company)