[json] UI for anyOf settings tooltips needs improvement

<!-- ⚠️⚠️ Do Not Delete This! bug_report_template ⚠️⚠️ --> <!-- Please read our Rules of Conduct: https://opensource.microsoft.com/codeofconduct/ --> <!-- Please search existing issues to avoid creating duplicates. --> <!-- Also please test using the latest insiders build to make sure your issue has not already been fixed: https://code.visualstudio.com/insiders/ --> <!-- Use Help > Report Issue to prefill these. --> Version: 1.50.1 (system setup) Commit: d2e414d9e4239a252d1ab117bd7067f125afd80a Date: 2020-10-13T15:06:15.712Z Electron: 9.2.1 Chrome: 83.0.4103.122 Node.js: 12.14.1 V8: 8.3.110.13-electron.0 OS: Windows_NT x64 10.0.19041 Note: I am aware of #92823, but this is a larger issue with settings tooltips for anyOf settings. I am about to go fix that specific case by writing extra description for that particular setting. Steps to Reproduce: 1. Go into the user settings page and search for font ligatures; click on the item there 2. You get this, and think you can only turn it on/off: [caption: "Enable/Disable font ligatures" in a tooltip for `editor.fontLigatures` on a line with `"editor.fontLigatures": null`]  3. Find out somehow that it allows strings and get this [also, assuming you think of mousing over it once you put the RHS in]? But what's a font-feature-settings [requires the user has domain knowledge of CSS]? [caption: "Explicit font-feature-settings" in a tooltip for `editor.fontLigatures` on a line with `"editor.fontLigatures": ""`]  Additionally, if you were to type in "editor.fontLigatures" and see the intellisense, it wouldn't help much: [caption: "Configures font ligatures or font features" in an intellisense box as a suggestion for "editor.font"] ![image](https://user-images.githubusercontent.com/6652840/98171869-45895f80-1ea5-11eb-…