Make port customizable from env variable (#8288)

app/server/appsmith-server/src/main/resources/application.properties

@@ -1,3 +1,5 @@
+server.port=${PORT:8080}
+
 # This property allows us to override beans during testing. This is useful when we want to set different configurations
 # and different parameters during test as compared to production. If this property is disabled, some tests will fail.
 spring.main.allow-bean-definition-overriding=true