Support Multiple Cost Object Types in Configuration

[petersutter]

What this PR does / why we need it:
This PR enhances the existing cost object configuration by allowing administrators to define multiple cost object types. Users can then select from these predefined types in the UI. The update introduces a dropdown menu where users can choose between different cost object types configured by the administrator.

Previously, the cost object value was stored under annotations["billing.gardener.cloud/costObject"] on the Project. With this update, the newly introduced type is stored under annotations["billing.gardener.cloud/costObjectType"].

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Release note:

Cost Object: You must migrate existing configurations to the new format. Previously, the configuration used `Values.global.dashboard.frontendConfig.costObject`. It should now be updated to `Values.global.dashboard.frontendConfig.costObjects`, which is a list of objects. Each object in this list must include a `type` property, alongside existing properties such as `title`, `description`, and `regex`.

Enhanced cost object configuration to support multiple cost object types. The selected type is now stored under `Project.annotations["billing.gardener.cloud/costObjectType"]`.

[grolu]

/lgtm apart from minor styling issue

[holgerkoser]

/lgtm