[feat] Enable deletion of custom fields in workspace (#4780)

**Context**
cf. feature request
[#4597](https://github.com/twentyhq/twenty/issues/4597)
Enables deletion of custom fields that aren't active nor of type
relation

Also 
1. renamed a misnamed file
2. deleted redundant hook BeforeDeleteOneField as it seemed best to move
the logic to the resolver instead

**How was it tested?**
Did not write unit tests as code is to be migrated (discussed with
@Weiko).
Locally tested.

---------

Co-authored-by: Marie Stoppa <mariestoppa@MacBook-Pro-de-Marie.local>

packages/twenty-server/src/engine/metadata-modules/relation-metadata/dtos/relation-metadata.dto.ts

@@ -17,7 +17,7 @@ import {
 
 import { ObjectMetadataDTO } from 'src/engine/metadata-modules/object-metadata/dtos/object-metadata.dto';
 import { RelationMetadataType } from 'src/engine/metadata-modules/relation-metadata/relation-metadata.entity';
-import { BeforeDeleteOneRelation } from 'src/engine/metadata-modules/relation-metadata/hooks/before-delete-one-field.hook';
+import { BeforeDeleteOneRelation } from 'src/engine/metadata-modules/relation-metadata/hooks/before-delete-one-relation.hook';
 
 registerEnumType(RelationMetadataType, {
   name: 'RelationMetadataType',