Chore(dot/parachain): Use `BlockNumber` type instead of `uint32` to store block number

[axaysagathiya]

Note

Need to merge in feat/parachain branch

Issue summary

• in some structs, we have a uint32 type field to store block numbers. We need to change them to use the BlockNumber type

• some known types to modify

  • ValidationParameters struct in dot/parachain/runtime/instance.go.
  • PersistedValidationData struct in dot/parachain/types/types.go.
    • We also have a redundant type in dot/parachain/available_data_fetching.go. Remove it.

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