Replace finders project pending_delete with deletion_in_progress and model scopes

What does this MR do and why?

Replace finders project pending_delete with deletion in progress

This is part 2 of #550627

Changes in This MR

Feature Flag

• Created use_deletion_in_progress_in_finders

Project Model

• Added deletion_in_progress scope - queries namespace state machine
• Added not_deletion_in_progress scope - inverse of above
• Kept existing pending_delete and without_deleted scopes unchanged

Core Finders

• ProjectsFinder

References

Closes #587867 (closed)

Query Plans

• deletion_in_progress scope: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/47749/commands/144146

• not_deletion_in_progress scope: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/48201/commands/145033

• ProjectsFinder (with FF on): https://console.postgres.ai/gitlab/gitlab-production-main/sessions/48201/commands/145034

• ProjectsFinder (with FF off): https://console.postgres.ai/gitlab/gitlab-production-main/sessions/48201/commands/145035

• /api/v4/projects (with FF on): https://console.postgres.ai/gitlab/gitlab-production-main/sessions/48201/commands/145036

• /api/v4/projects (with FF off): https://console.postgres.ai/gitlab/gitlab-production-main/sessions/48201/commands/145037

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Before	After

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