Kernel/SDK/Installer: Add a new smart-rollup command to merge setup file

What

The smart-rollup-installer has now a new command to merge multiple setup files together

Why

As Etherlink and Tezlink are expected to run on the same rollup, we should be able to specify the bootstrap account for Etherlink and others bootstrap accounts for Tezlink

Manually testing the MR

There is a new unit test that checks the feature and you can just make build in src/kernel_sdk and then try to use the binary on multiple setup file and verify that the new setup file is the concatenation of both, for example

smart-rollup-installer merge-setup-files --output ~/merged_config.yaml -S ~/tezos/etherlink/config/sequencer.yaml -S ~/tezos/etherlink/config/ghostnet.yaml

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).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR