[6131][ADD] purchase_deposit_separate_valuation

[kanda999]

6131

[AungKoKoLin1997]

@kanda999 Can you please fix pre-commit issue first before I review?

[kanda999]

This PR will be closed due to a policy change (Task 6131).

Reason: The method for freezing inventory valuation (Separate Valuation Mode + automatic transfer of remaining GRNI)
is no longer necessary for the time being, and we have decided to proceed first with the rate limit order method for #147 purchase_deposit_currency. With the limit order method, the invoice amount itself is adjusted to match the actual payment amount,
eliminating the need to suppress the price difference SVL.

In case the requirement resurfaces, the branch 16.0-add-purchase_deposit_separate_valuation will
be retained (it can also be restored from refs/pull/148/head).

Handover Notes for Resumption:

• Suppressing _apply_price_difference and the automatic transfer of the remaining GRNI via _sync_sep_val_grni_adjustment
  are a set of actions. If you only implement the suppression, the GRNI will not close.
• Adjustment journal entries are only generated once the PO is marked as “fully invoiced,” and are regenerated via
  delete + create with each status change. If the entries have been cleared, they cannot be deleted and will result in a UserError.
• On staging (axlstest12), Separate Valuation Mode was enabled for 86 POs, and
  15 adjustment journal entries (all posted but not cleared) had been generated.

The merge line for this PR has also been removed from /odoo/code/repos.yml (staging).