Allow disabling the root_id prefix from custom role definitions names

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### Description

Allow discarding the root_id prefix for custom role definitions.

#### Is your feature request related to a problem?

I'm part of a platform team which services product teams within my company. The custom role definitions we define and create via this module, are exposed to product teams. While the naming convention "[some-cryptic-root-id] real-resource-name" is useful for resources managed by the platform team, I would much prefer to use a prettier name without a prefix for custom role definitions consumed by product teams.

#### Describe the solution you'd like

Some input variable in the module which would disable the root_id prefix for custom role definition names.

#### Additional context

Start by locating the module logic that creates custom role definitions and applies the root_id prefix. Check how module inputs are defined and confirm that disabling the new option produces names without the prefix while preserving the current default behavior.

Written by the indexing model from the issue text.