remove remaining uint32/uint64/string scalar types if possible

[ylecornec]

Continue what was started in PR #11283, and replace basic graphql scalars by custom ones to have more type information in the GraphQL schema and be able to select decoders automatically with graphql_ppx.

After discussion on PR #11517, there may be third party consumers of the GraphQL api that could be affected by this change.

• [ ] declare custom scalars :
  • [x] For the common part of the graphql schema PRs (#11574) and (#11580)
  • [ ] For the develop part of the graphql schema. (See #11560)
• [ ] open PR with the breaking changes to develop only.