[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/field-metadata/dtos/delete-field.input.ts

@@ -0,0 +1,9 @@
+import { InputType, ID } from '@nestjs/graphql';
+
+import { IDField } from '@ptc-org/nestjs-query-graphql';
+
+@InputType()
+export class DeleteOneFieldInput {
+  @IDField(() => ID, { description: 'The id of the field to delete.' })
+  id!: string;
+}