Allow merge_with_module_tags for all resources

### Check for previous/existing GitHub issues

- [x] I have checked for previous/existing GitHub issues

### Issue Type?

Feature Request

### (Optional) Module Version

12.2

### (Optional) Correlation Id

_No response_

### Description

Some resources feature a useful property `merge_with_module_tags` while others (most) only allow to override by passing in a complete set of tags.

The only places that actually expose `merge_with_module_tags` are:

* `virtual_hubs[*].private_dns_resolver.inbound_endpoints[*].merge_with_module_tags`
* `virtual_hubs[*].private_dns_resolver.outbound_endpoints[*].merge_with_module_tags`
* `virtual_hubs[*].private_dns_resolver.outbound_endpoints[*].forwarding_ruleset[*].merge_with_module_tags`

Everything else only has a raw `tags` map (no merge flag, so effectively override)

Especially when deploying using the ALZ accelerator, to keep code DRY, providing a `merge_with_module_tags` option for all taggable blocks is much desired, with a default of `true` so base/module tags are always merged with per-resource tags unless explicitly turned off.

No files, tests, or entry points are named. Start by locating the existing merge_with_module_tags definitions and all resource tag blocks, then determine how tag merging is currently tested. Done means taggable blocks support the option with a default of true and an explicit opt-out, with coverage for representative resources.

Written by the indexing model from the issue text.