Snoop: allow less benchmarks than the size of the data for michelson

Context

Fix #3931

Snoop fails when trying to run less benchmarks than the number of given data for michelson benchmarks. This MR fixes this issue

Manually testing the MR

Run a benchmark that uses generated michelson data, for instance :

./octez-snoop benchmark proto/alpha/encoding/ENCODING_MICHELINE and save to foo.workload --config-file config.json --bench-num 1

Where config.json specifies the location of the generated code, as given by tezt for example. This command fails before the patch, but succeeds with it.

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