Prover: generated config samples

[AlexandreBelling]

This PR proposes having the sample config-files generated from a template instead of having them manually maintained. We are always free to modify them but modification will be flags by the CI and they won't be mergeable from main.

• This forces consistency of their values across different files
• Ensure we don't commit local filepaths which could be sensitive informations

Checklist

• I wrote new tests for my new core changes.
• I have successfully ran tests, style checker and build against my new changes locally.
• If this change is deployed to any environment (including Devnet), E2E test coverage exists or is included in this
  PR.
• I have informed the team of any breaking changes if there are any.

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Note

Medium Risk
Primarily restructures and rewrites the canonical sample config files (including mainnet/staging modes and allowed-circuit bitmasks), which could affect any workflows that consume these samples. Adds a new generator invoked via go generate, so CI/build steps that validate generated outputs may fail if the generator/template diverge.

Overview
Sample prover configs are now generated. Adds config_sample_generator (template + Go program) and wires it into prover/config/config.go via //go:generate to produce the committed config-*.toml files.

Regenerates/normalizes the sample configs for devnet, e2e, sepolia, and mainnet (version bump to 6.1.5, removes machine-specific paths, standardizes controller/requests settings, and updates prover_mode/is_allowed_circuit_id/verifier_id values), adds a prover/config/.gitignore to ignore non-sample .toml files, and removes config-integration-benchmark.toml.

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