[Module Catalog] Remove the old way of fetching all ModuleTemplates

[nesmabadr]

Description

We still support the old way of listing all the ModuleTemplates and then filtering them by the channel if there is no ModuleReleaseMeta existing for this module. After all modules teams have their ModuleReleaseMeta CRs deployed to the KCP, we need to remove this old code.

Reasons

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Acceptance Criteria

• Remove the code which lists all ModuleTemplates and only support the usage of ModuleReleaseMeta
• Remove the old E2E tests which run without the ModuleReleaseMeta

Feature Testing

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Testing approach

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Attachments

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