[BUG][Swift5] Parameters unexpectedly base64-encoded.

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• Have you tested with the latest master to confirm the issue still exists?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

With the swift5 generator version5.4.0, JSONEncodables default to Data.JSONEncodable which uses base64EncodedString. It seems like this should not be intentional given that we also have these extensions which apparently are not being used as a result.

extension Bool: JSONEncodable {}
extension Float: JSONEncodable {}
extension Int: JSONEncodable {}
// etc

extension JSONEncodable {
    func encodeToJSON() -> Any { self }
}

The API we are using does not expect base64-encoded params and this is leading to bad request errors (400). This problem was introduced in 5.4.0 after upgrading from 5.3.0.

openapi-generator version

5.4.0. This appears to be a regression.

Steps to reproduce

Generate against a spec with an integer query parameter and observe that it gets base64-encoded.

e.g. expected: limit=100, got: limit=MTAw

Related issues/PRs

I believe this PR introduced the issue:

https://github.com/RitualCo/ios/pull/2725

Suggest a fix

It can be patched by doing

extension JSONEncodable where Self == Int {
  func encodeToJSON() -> Any { return self as Any }
}
// etc

Start with the Swift5 generator output, especially JSONEncodable and the integer query-parameter serialization described in the report. Reproduce the 5.4.0 behavior with a generated client and an integer parameter; done means values such as 100 remain 100 rather than becoming MTAw, with regression coverage if the repository provides a suitable test entry point.