Add Gpr tasks to build and run main subprograms

Add a Language Server extension to get the project main sources (glsMains request).
Add a Language Server extension to get the project main executables (glsExecutables request).
Activate the extension when Gpr or Ada sources are present in the current directory or sub-directory (only 1 level lookup).
Add tests to the VS Code extension test-suite, testing the alsCheckSyntax, glsMains and glsExecutables requests.

Author: abdellah257

Diff for: doc/README.md

@@ -45,3 +45,4 @@ related resources.
  * [Reference kinds](reference_kinds.md)
  * [Show Dependencies](show_dependencies.md)
  * [Check Syntax](check_syntax.md)
+ * [Executables](executables.md)

Diff for: doc/executables.md

@@ -0,0 +1,39 @@
+# Executables
+
+## Short introduction
+
+This implements a functionality to query the mains and the executables for a multi targets project.
+
+## Capabilities 
+
+We provide the Build and Run tasks for specific targets in a GPR Projects.
+
+To check these tasks :
+- click :  `Ctrl + Shift + P `.
+- Select  `Run Tasks` , then Select  `GPR Tasks`.
+
+## Change description
+
+We introduce two requests, the first one:
+
+    method: `glsMains`
+
+Which provides the mains for the project, with a response type:
+
+```typesript
+type GlsMainResult = {
+    mains: string[];
+};
+```
+
+The second one is:
+
+    method: `glsExecutables`
+
+Which provides the executables for the project, with a response type:
+
+```typesript
+type GlsExecutableResult = {
+    executables: string[];
+};
+```

Diff for: integration/vscode/ada/.gitignore

@@ -2,3 +2,4 @@ node_modules
 .vsix
 out
 .vscode-test
+**/obj

Diff for: integration/vscode/ada/.vscode/launch.json

@@ -18,10 +18,8 @@
             "runtimeExecutable": "${execPath}",
             "args": [
                 "--extensionDevelopmentPath=${workspaceFolder}",
-                "--extensionTestsPath=${workspaceFolder}/out/test/suite/index"
-            ],
-            "outFiles": [
-                "${workspaceFolder}/out/test/**/*.js"
+                "--extensionTestsPath=${workspaceFolder}/out/test/suite/index",
+                "${workspaceFolder}/test/SampleProject"
             ],
             "preLaunchTask": "npm: pretest"
         }

Diff for: integration/vscode/ada/package.json

@@ -18,9 +18,14 @@
     "activationEvents": [
         "onLanguage:ada",
         "onLanguage:gpr",
+        "workspaceContains:*.gpr",
+        "workspaceContains:*/*.gpr",
+        "workspaceContains:*.ad[bs]",
+        "workspaceContains:*/*.ad[bs]",
+        "workspaceContains:alire.toml",
         "onCommand:workbench.action.tasks.runTask"
     ],
-    "main": "./out/extension",
+    "main": "./out/src/extension",
     "icon": "icons/ada.png",
     "bugs": "https://github.com/AdaCore/ada_language_server/issues",
     "repository": {
@@ -437,6 +442,23 @@
                         "description": "Extra command arguments"
                     }
                 }
+            },
+            {
+                "type": "GPR Tasks",
+                "required": [
+                    "projectFile",
+                    "mainFile"
+                ],
+                "properties": {
+                    "projectFile": {
+                        "type": "string",
+                        "description": "The project file"
+                    },
+                    "executable": {
+                        "type": "string",
+                        "description": "The main file"
+                    }
+                }
             }
         ],
         "commands": [