Refactor: consolidate AWS/Azure config assembly into shared resolvers

[bencehezso]

Summary

handle_aws and handle_azure had each grown to ~200 lines that assembled the same config dict up to six different ways (config file / non-interactive / profile or cli / manual prompts), repeating the name-fallback expression five times and duplicating the boto3 credential block twice. This PR extracts a config resolution layer so each credential source has one job and the final config is built in one place.

What changed

• utils/utils.py — two shared helpers:
  • resolve_name(args) — the --name → timestamped-default logic (was inlined 5×).
  • build_config(...) — assembles the final assessment config envelope (was rebuilt 6×).
• main.py — per-source resolvers that each return a providerDetails dict:
  • AWS: _aws_provider_from_profile, _aws_provider_from_env, _aws_provider_from_prompt
  • Azure: _azure_cli_credential, _azure_provider_noninteractive, _azure_provider_from_cli, _azure_provider_from_prompt
  • A small ConfigError signal lets each caller decide abort semantics (sys.exit(codes.CONFIG) in non-interactive/CI, plain return interactively).
  • handle_aws / handle_azure are now thin dispatchers (~200 → ~55 lines each): pick the source, resolve inputs, call a resolver, build_config(...) → run_assessment(...).

User-facing impact

None intended. CLI flags, prompt order and wording, env-var handling, exit codes,
and generated config shape are all preserved. Two small consistency fixes ride along:

• AWS profile error messages are unified to the richer wording both paths used inconsistently.
• The interactive Azure --cli error path now returns cleanly instead of
  falling through to run_assessment({}) with an empty config.