inefficient regex for domain validation (exp. complexity)

https://gitlab.com/tezos-domains/client/-/blob/071e9a1d36c594504da413da45055c157166a75a/packages/core/src/validator/validators.ts#L22

this freezes our app:

• when adding a label like aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!
• when visiting https://staging-app.tezos.domains/domain/aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa!.edo