Create vaadin-flow-spring-boot-starter artifact in platform

[mshabarov]

The goal is to have an equivalent of vaadin-spring-boot-starter for pure Flow/Java apps using free components and embed vaadin-core dependencies into it. Self-sufficient for Spring Boot Flow app.

Create vaadin-flow-core-spring-boot-starter in platform that includes:

• flow-components (Create flow-components artifact in platform #8168)
• vaadin-spring (exists)
• spring-boot-starter-web (exists)

We may want to replace flow deps in vaadin-core-internal with just flow.

Note: enableReact value default (true) is kept same as in the existing vaadin-spring-boot-starter.