Initial terminal ui implementation

- This commit adds proof of concept work for terminal ui as is.
- Some things work, some don't but we need to start from somewhere.
  Further development continues in a main.
- Essentially we are starting to have enough so that it merits to
  move all this work into a main repo.
- Everything new is kept under org.springframework.shell.component.view
  and will get revisiter later to find correct locations for some classes.
- Catalog sample has been modified to provide "showcase" app for
  terminal ui features. This is a start while it already contains
  some usefull scenarios.
- Relates spring-projects#800
- Relates spring-projects#801
- Relates spring-projects#802
- Relates spring-projects#803
- Relates spring-projects#804
- Relates spring-projects#805
- Relates spring-projects#806
- Relates spring-projects#807
- Relates spring-projects#808
- Relates spring-projects#809
- Relates spring-projects#810
- Relates spring-projects#811

.vscode/launch.json

@@ -94,6 +94,13 @@
             "mainClass": "org.springframework.shell.samples.SpringShellSample",
             "projectName": "spring-shell-sample-e2e",
             "args": "e2e reg exit-code --arg1 fun"
+        },
+        {
+            "type": "java",
+            "name": "catalog",
+            "request": "launch",
+            "mainClass": "org.springframework.shell.samples.catalog.SpringShellApplication",
+            "projectName": "spring-shell-sample-catalog"
         }
     ]
 }

.vscode/settings.json

@@ -13,5 +13,6 @@
         "checkstyle.header.file": "https://raw.githubusercontent.com/spring-cloud/spring-cloud-dataflow-build/main/spring-cloud-dataflow-build-tools/src/main/resources/checkstyle-header.txt"
     },
     "java.checkstyle.version": "8.29",
-    "java.configuration.maven.notCoveredPluginExecutionSeverity": "ignore"
+    "java.configuration.maven.notCoveredPluginExecutionSeverity": "ignore",
+    "java.jdt.ls.vmargs": "-XX:+UseParallelGC -XX:GCTimeRatio=4 -XX:AdaptiveSizePolicyWeight=90 -Dsun.zip.disableMemoryMapping=true -Xmx2G -Xms100m -Xlog:disable"
 }

spring-shell-core/spring-shell-core.gradle

@@ -10,11 +10,13 @@ dependencies {
 	api('org.springframework:spring-core')
 	api('org.springframework.boot:spring-boot-starter-validation')
 	api('org.springframework:spring-messaging')
+	api('io.projectreactor:reactor-core')
 	api('org.jline:jline')
 	api('org.antlr:ST4')
 	api('commons-io:commons-io')
 	compileOnly 'com.google.code.findbugs:jsr305'
 	testImplementation 'org.springframework.boot:spring-boot-starter-test'
 	testImplementation 'org.awaitility:awaitility'
 	testImplementation 'com.google.jimfs:jimfs'
+	testImplementation 'io.projectreactor:reactor-test'
 }