Rename PostService to MenuPostService

[crazytonyli]

Description

The "sync" functions in PostService are only used in the Menu feature. This PR renames the PostService type to MenuPostService to avoid the sync function being used in other features. The sync functions fetch every single page when used to fetch pages, and fetch paginated posts when used to fetch posts, which I think is not something we'd normally want.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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	Version	PR #25049
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[kean]

The sync functions fetch every single page when used to fetch pages, and fetch paginated posts when used to fetch posts, which I think is not something we'd normally want.

Definitely not.

The Menu* code is something I would suggest to keep as Objective-C potentially indefinitely unless there is a need to redesign it.

[crazytonyli]

The Menu* code is something I would suggest to keep as Objective-C

Yeah, I don't plan to change that part. It's rarely updated.