Make `TransactionExtension` tuple of tuple transparent for implication (#7028)

Currently `(A, B, C)` and `((A, B), C)` change the order of implications
in the transaction extension pipeline. This order is not accessible in
the metadata, because the metadata is just a vector of transaction
extension, the nested structure is not visible.

This PR make the implementation for tuple of `TransactionExtension`
better for tuple of tuple. `(A, B, C)` and `((A, B), C)` don't change
the implication for the validation A.

This is a breaking change but only when using the trait
`TransactionExtension` the code implementing the trait is not breaking
(surprising rust behavior but fine).

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Co-authored-by: command-bot <>
Co-authored-by: Bastian Köcher <[email protected]>