Ruby: Add option for old path parameter behaviour

[ccouzens]

The OpenAPI standard is to percent encode special characters such as
slashes, hashes and question marks when they appear in path parameters.

The Ruby client generator was buggy. It did not encode these characters.
So a few days ago I fixed it.
#3039

Unfortunately, some projects rely on the incorrect behaviour.
In particular, they need slashes not to be escaped.

For example:
#3119

I've added an additional property to the ruby generator to undo the
escaping of slashes in path parameters. This will enable those projects
to continue to make use of the Ruby client code generator.
--additional-properties compatibilitySlashesInPathParameters

I'd suggest the long term plan for projects that need this behaviour
should be to work with the OpenAPI Specification writers to support
marking certain path parameters as allowing slashes.

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@cliffano @zlx @autopp

Description of the PR

Fix #3119
See above

[dkliban]

@ccouzens I test this PR and it does not solve the problem all the way. The URL that is generated by the api_client::build_request_url now contains and extra '/' on the front. The server always returns a 404. This behavior is very similar to #2702. I think changing the order of substitution should fix the problem.

[ccouzens]

@dkliban I've swapped the order like you suggested. That should fix the double slash problem

[ccouzens]

I'm closing this because #3204 solved the issue instead.