[Feat]: Resolving OU based parameters when not targeting OU

### Describe the feature

When targeting accounts with tags, we would need to be able to give parameters to a set of accounts.

```
targets:
- tags:
tag1: value
tag2: value2
regions: [eu-west-1, eu-north-1]
```

The accounts are put into separate OU's for examples sake /prod and /dev

Pipeline repository would have files, and these would be matched to the template according to the OU the account belongs to

```
params/
├── global.yml
├── ou-123-445678.yml or prod.yml
└── ou-123-567890.yml or dev.yml
```

I mentioned this in issue #294 and Simon asked to open a separate ticket - so here it is.

### Use Case

We have a client setup that targets with tags (if you ask why, I can give you a legacy answer before version 3.2.0 came out).

When targeting accounts with tags, giving separate parameters to accounts can only currently be done with account.yml or global.yml

`global.yml
└───deployment_account_region.yml (e.g. global_eu-west-1.yml)
└───ou.yml (e.g. ou-1a2b-3c4d5e.yml)
└───ou_region.yml (e.g. ou-1a2b-3c4d5e_eu-west-1.yml)
└───account.yml (e.g. dev-account-1.yml)
└───account_region.yml (e.g. dev-account-1_eu-west-1.yml)`

It would make management of accounts in this setup easier, when one can have one type of account in its own OU (ex. /dev) and parameters would come from ou.yml, instead of having account.yml for each account.

### Proposed Solution

Script generating parameters could check the OU the account belongs to and check if OU parameter file exists and use that.

### Acknowledgements

- [ ] I may be able to implement this feature request

Start by locating the script that generates parameters and trace the existing account and OU resolution flow. Compare the current params/global.yml and account.yml handling with the proposed OU-named files, then verify that tag-targeted accounts can resolve OU parameters while retaining the existing hierarchy and regional behavior.

Written by the indexing model from the issue text.