chore: remove vue/compat and complete Vue 3 migration (#7133)

* chore: remove custom `compatConfig` settings

* chore: remove `vue-compat` and adjust webpack config

* chore: explicitly define Vue feature flags

* fix: `_data` property moved to `_.data`

* fix(e2e): revert to original test procedures

* refactor: replace final instances of `$set`

* refactor: remove `Vue` imports from tests

* refactor: `Vue.ref()` -> `ref()`

* refactor: actually push the changes...

* test: replace unit test with e2e test

* test: remove test as it's already covered by e2e

* fix(test): use `$ref`s instead of `$children`

* test(fix): more `$refs`

* fix(test): more `$refs`

* fix(test): use `$refs` in InspectorStyles tests

* fix(SearchComponent): use `$attrs` correctly

---------

Co-authored-by: Scott Bell <scott@traclabs.com>

.webpack/webpack.common.js

@@ -77,8 +77,7 @@ const config = {
       MCT: path.join(projectRootDir, 'src/MCT'),
       testUtils: path.join(projectRootDir, 'src/utils/testUtils.js'),
       objectUtils: path.join(projectRootDir, 'src/api/objects/object-utils.js'),
-      utils: path.join(projectRootDir, 'src/utils'),
-      vue: path.join(projectRootDir, 'node_modules/@vue/compat/dist/vue.esm-bundler.js'),
+      utils: path.join(projectRootDir, 'src/utils')
     }
   },
   plugins: [
@@ -86,7 +85,9 @@ const config = {
       __OPENMCT_VERSION__: `'${packageDefinition.version}'`,
       __OPENMCT_BUILD_DATE__: `'${new Date()}'`,
       __OPENMCT_REVISION__: `'${gitRevision}'`,
-      __OPENMCT_BUILD_BRANCH__: `'${gitBranch}'`
+      __OPENMCT_BUILD_BRANCH__: `'${gitBranch}'`,
+      __VUE_OPTIONS_API__: true, // enable/disable Options API support, default: true
+      __VUE_PROD_DEVTOOLS__: false // enable/disable devtools support in production, default: false
     }),
     new VueLoaderPlugin(),
     new CopyWebpackPlugin({
@@ -115,7 +116,7 @@ const config = {
     new webpack.BannerPlugin({
       test: /.*Theme\.css$/,
       raw: true,
-      banner: '@charset "UTF-8";',
+      banner: '@charset "UTF-8";'
     })
   ],
   module: {
@@ -142,10 +143,7 @@ const config = {
         options: {
           compilerOptions: {
             hoistStatic: false,
-            whitespace: 'preserve',
-            compatConfig: {
-              MODE: 2
-            }
+            whitespace: 'preserve'
           }
         }
       },