Relocate projects to spring-boot-project

Move projects to better reflect the way that Spring Boot is released.

The following projects are under `spring-boot-project`:

  - `spring-boot`
  - `spring-boot-autoconfigure`
  - `spring-boot-tools`
  - `spring-boot-starters`
  - `spring-boot-actuator`
  - `spring-boot-actuator-autoconfigure`
  - `spring-boot-test`
  - `spring-boot-test-autoconfigure`
  - `spring-boot-devtools`
  - `spring-boot-cli`
  - `spring-boot-docs`

See gh-9316

spring-boot-project/spring-boot-cli/test-samples/spock.groovy

@@ -0,0 +1,12 @@
+class HelloSpock extends Specification {
+	def "length of Spock's and his friends' names"() {
+		expect:
+		name.size() == length
+
+		where:
+		name     | length
+		"Spock"  | 5
+		"Kirk"   | 4
+		"Scotty" | 6
+	}
+}