Add spring-boot-reactor to reactive starters

This commit adds the "spring-boot-reactor" module as a dependency to
reactive starters. While this was already the case for many starters,
this module was missing from GraphQL, RSocket, WebClient and WebFlux.

Closes gh-49332

starter/spring-boot-starter-graphql/build.gradle

@@ -24,5 +24,6 @@ dependencies {
 	api(project(":starter:spring-boot-starter"))
 	api(project(":starter:spring-boot-starter-jackson"))
 
+	api(project(":module:spring-boot-reactor"))
 	api(project(":module:spring-boot-graphql"))
 }

starter/spring-boot-starter-rsocket/build.gradle

@@ -25,6 +25,7 @@ dependencies {
 	api(project(":starter:spring-boot-starter-jackson"))
 	api(project(":starter:spring-boot-starter-reactor-netty"))
 
+	api(project(":module:spring-boot-reactor"))
 	api(project(":module:spring-boot-rsocket"))
 
 	api("io.rsocket:rsocket-transport-netty")

starter/spring-boot-starter-webclient/build.gradle

@@ -24,6 +24,7 @@ dependencies {
 	api(project(":starter:spring-boot-starter"))
 	api(project(":starter:spring-boot-starter-jackson"))
 
+	api(project(":module:spring-boot-reactor"))
 	api(project(":module:spring-boot-webclient"))
 
 	api("io.projectreactor.netty:reactor-netty-http")

starter/spring-boot-starter-webflux/build.gradle

@@ -25,5 +25,6 @@ dependencies {
 	api(project(":starter:spring-boot-starter-jackson"))
 	api(project(":starter:spring-boot-starter-reactor-netty"))
 
+	api(project(":module:spring-boot-reactor"))
 	api(project(":module:spring-boot-webflux"))
 }