etherlink: with an admin contract update the sequencer key

Context

A L1 contract sets via a inbox message the sequencer for a rollup.

Manually testing the MR

try to originate an evm rollup and then adds a sequencer key via the smart contract. Now you must uses the sequencer to produce blueprint.

fix #6837 (closed)

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
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