test: modernize the RSpec suite and cover the workflow logic

[tas50]

What

spec/spec_helper.rb was an empty license header — no requires, no RSpec.configure, and nothing in .rspec to load it. Every spec file had to require its own dependencies, and none of the guardrails that catch stale tests were on.

This wires the suite up the way the rest of our drivers do:

• .rspec passes --require spec_helper, so the helper is the single place that loads the driver and its Test Kitchen dummies.
• spec_helper turns on verify_partial_doubles, disable_monkey_patching!, expect-only syntax, raise_errors_for_deprecations!, and random ordering with a printed seed.
• spec/support/vro_doubles.rb builds verifying doubles for the slice of the vcoworkflows API this driver touches. If vcoworkflows renames token or drops output_parameters, the suite fails instead of passing against a stub that no longer matches the real object.
• Specs are no longer excluded from cookstyle, so they are held to the same style as lib/.

Coverage

The old suite checked #create and #destroy by stubbing the driver's own methods and asserting they were called. That proves the methods call each other; it proves nothing about what we actually send to vRO. There are now end-to-end examples that stub only at the VcoWorkflows::Workflow boundary and assert the real behaviour: which workflow gets looked up, that configured create and destroy parameters are pushed to it, that server_id reaches the destroy workflow, and that create output lands in instance state.

New coverage aimed at the branches where bugs actually hide:

• the poll loop in #wait_for_workflow — how many times the token is re-read, that it sleeps two seconds between polls, that it does not sleep when the run has already finished, and that a real elapsed timeout fires
• request_timeout showing up in the timeout message when it is not the default
• #set_workflow_parameters stringifying symbol keys, passing non-string values through, and no-opping on an empty hash
• #output_parameter_value stringifying numbers and unset values
• vro_disable_ssl_verify reaching VcoWorkflows::Config
• #execute_create_workflow neither validating output nor writing state when the run failed
• memoization of vro_config, vro_client, and output_parameters

Also drops a Struct.new assigned to a top-level constant inside an example — it leaked a constant into the whole suite and warned on redefinition — and corrects the spec path in CONTRIBUTING.md, which pointed at a file that does not exist.

No change to lib/. 51 examples became 77.

Verification

$ bundle exec cookstyle --chefstyle
Inspecting 8 files
........

8 files inspected, no offenses detected

$ bundle exec rake test
77 examples, 0 failures

[tas50]

Pushed an extra commit dropping the unused webmock dev dependency. It was never required by anything in spec/, and cookstyle 9.0.0 (released since the last merge here) flags the extra spacing on that Gemfile line under Layout/ExtraSpacing — so main went red on its own the moment cookstyle 9 shipped, and every PR inherits it. Same one-line commit is on #46 so both can go green independently of merge order.