Update wearables and skins max size

## Description

The current upload size limit for the Skin Category is set at 2MB, and the wearable size (others than skins) is restricted to 2MB as well. We need to apply [this](https://decentraland.org/governance/proposal/?id=7e8c2640-37d1-11ed-b361-67b98a1da2c8) proposal, to upload size for the Skin Category from 2MB to 8MB.

# Update Validation Rules and Constants for Item Sizes

- Define the following:
- The maximum size for wearables is 2 MB.
- The maximum size for a skin is 8 MB.
- The maximum size for a thumbnail is 1 MB.
- The maximum size for emotes is 2 MB.
- The combined size of a wearable plus a thumbnail is 3 MB.
- The size for a skin plus a thumbnail is 9 MB.

- [x] Update Validation in [content-validator](https://github.com/decentraland/content-validator/blob/main/src/validations/items/items.ts) and its [constants](https://github.com/decentraland/content-validator/blob/main/src/validations/ADR51.ts) ([PR](https://github.com/decentraland/content-validator/pull/294))
- [x] Add Necessary Constants in [builder-client](https://github.com/decentraland/builder-client) in the file [src/files/constants.ts](https://github.com/decentraland/builder-client/blob/main/src/files/constants.ts)
- [ ] Update Validation Processes in Builder (Current [PR](https://github.com/decentraland/builder/pull/3051)):
- [x] [CreateAndEditMultipleItemsModal](https://github.com/decentraland/builder/blob/master/src/components/Modals/CreateAndEditMultipleItemsModal/CreateAndEditMultipleItemsModal.tsx)
- [x] [ImportStep](https://github.com/decentraland/builder/blob/master/src/components/Modals/CreateSingleItemModal/ImportStep/ImportStep.tsx)
- [x] [modules/item/sagas.ts](https://github.com/decentraland/builder/blob/master/src/modules/item/sagas.ts)
- [x] Update all error messages, currently they only specify one file size. Mainly [here](https://github.com/decentraland/builder/blob/master/src/modules/item/errors.tsx)
- [x] Update item editor
- [ ] Review UX/UI error messages

**Create ADR for Size Updates:**
- [ ] Create an ADR documenting the size updates, referring to [ADR-51](https://adr.decentraland.org/adr/ADR-51) and [ADR-45](https://adr.decentraland.org/adr/ADR-45) for this update.

# Link
- [Proposal](https://decentraland.org/governance/proposal/?id=7e8c2640-37d1-11ed-b361-67b98a1da2c8)
- [Shape up](https://www.notion.so/decentraland/Increase-Skin-Full-Character-Category-testing-server-upload-size-from-2MB-to-8MB-35b9ec3682294aadae81a8f52dbda8c8?pvs=4)
- [Canny](https://decentraland.canny.io/builder/p/increase-skin-full-character-category-testing-server-upload-size-from-2mb-to-8mb)

Review the remaining work in src/components/Modals/CreateAndEditMultipleItemsModal/CreateAndEditMultipleItemsModal.tsx, src/components/Modals/CreateSingleItemModal/ImportStep/ImportStep.tsx, src/modules/item/sagas.ts, and src/modules/item/errors.tsx, considering the current builder PR. Then read ADR-51 and ADR-45 to define what the missing ADR and UX/UI review must cover; done means the outstanding checklist items are addressed and the size messages and documentation are consistent.

Written by the indexing model from the issue text.