Fix multi-part binary array form parameters for Spring Boot and Spring Cloud templates

Created by: rbrincke

Multi-part binary array strings as outlined in #3139 (closed) resulted in MultipartFile rather than List<MultipartFile>. This PR attempts to resolve this by adjusting the templates for Spring Boot and Spring Cloud. Changes to these templates include:

• wrap contents in List where appropriate
• use defined description rather than a hard-coded one
• use defined RequestPart name rather than hard-coded one

Two tests have been added: one for spring-boot and one for spring-cloud.

Resolve #3139 (closed)

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