ref: one codebase for hover tooltip and freezed tooltip

- rename variables for URL template, use templateSrv to render URL links
- fix visibility of tooltip items and url template help popup whe the light theme is used
- rework Tooltip settings pane, organize tooltip editor fields
- rename properties in panel config, implement migration logic for legacy configuration
- close button for the frozen tooltip
- use relative positioning for proper page scrolling

jest.config.js

@@ -0,0 +1,13 @@
+module.exports = {
+    verbose: false,
+    transform: {
+        '^.+\\.(ts|tsx)$': 'ts-jest',
+    },
+    moduleDirectories: ['node_modules'],
+    roots: ['<rootDir>/src'],
+    testRegex: '(\\.|/)(test)\\.(jsx?|tsx?)$',
+    moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json'],
+    //setupFiles: ['jest-canvas-mock', './public/test/jest-shim.ts', './public/test/jest-setup.ts'],
+    //snapshotSerializers: ['enzyme-to-json/serializer'],
+    globals: { 'ts-jest': { isolatedModules: true } },
+};