refactor: use common functionality to validate account number

[FHenry]

Please provide enough information so that others can review your pull request:

In France we have chart of account where the same Account number can be use as Liability or as Asset ( the root_type do not exists like that but in France, it imply other definition and meaning but we try to find a way to allow proper French accountancy in ERPNext)

We can understand that add root_type to the check the uniqueness of a Account number may not please all country accountancy rules.
So we can also change the PR to always send root_type as parameters and not use it for standard/core test of uniqueness but add @erpnext.allow_regional on the validate_account_number() function.
Like that we can override it in ERPNext France app

Explain the details for making this change. What existing problem does the pull request solve?

This PR make two changes :

Use the same method/function on Account creation as on Account update to check the validity of the account number
Send root_type as parameters to validate_account_number() to check account number uniqueness by company and root_type

no-docs

Following #42279

[stale]

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[umairsy]

@ruthra-kumar could we review this PR in reference to discussion in the previous PR? This will help us make ERPNext France comprehensive. It's already listed on FC Marketplace and available for installation.

Cc: @vorasmit