Replace all api calls that retrieve LanguageKey by the a new APIs that return LanguageVariable (Content)

[fabrizzio-dotCMS]

Parent Issue

#25603

User Story

Write a new API Method to retrieve all Language Variables as lightly as possible. No contentlet additional info should be making it into the returned object. Only identifier, key, value, and language.
This way the resulting method can be cached with a smaller memory footprint. Once this method is in place and caching is properly handled we need to identify the actual use of the old APIs and replace them with the respective calls to the new ones. So we only rely on the language variables stored as content.
This method should ignore permissions and should content state (working or live) any LanguageVariable should be returned.

Acceptance Criteria

After completing this task No use of the old LanguageKey API should remain active in code.
The Old APIS should be marked as deprecated. So they can be easily identified shortly for removal.
The new APIs method will make it possible to load and cache all Language Variables despite of state and permissions

Proposed Objective

Core Features

Proposed Priority

Priority 3 - Average

External Links... Slack Conversations, Support Tickets, Figma Designs, etc.

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Assumptions & Initiation Needs

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Quality Assurance Notes & Workarounds

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Sub-Tasks & Estimates

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