feat: Add signatureHelp and hover providers to monaco (#1178)

Corresponds with deephaven/deephaven-core#3607

This adds signatureHelp and hover providers if the JS API supports the
corresponding requests

SignatureHelp is provided when you type a method and then type the `(`
character. There's also probably a keybinding in monaco to trigger it,
but I'm not sure what it is.

Hover provided when you hover anything

Needs to use [my core
branch](https://github.com/mattrunyon/deephaven-core/tree/lsp-improvements)
to test. After pulling that branch, will need to build/install the
Python server using the following commands

```
./gradlew :py-server:assemble :py-embedded-server:assemble
pip install --force-reinstall py/server/build/wheel/deephaven_core-0.23.0-py3-none-any.whl py/embedded-server/build/wheel/deephaven_server-0.23.0-py3-none-any.whl
```

Then start using one of these commands. Groovy provided just to show it
doesn't break anything in Groovy. There is no autocomplete in Python
notebooks if you are using a Groovy worker.

```
./gradlew server-jetty-app:run # Python
START_OPTS="-Ddeephaven.console.type=groovy" ./gradlew server-jetty-app:run # Groovy
```

Author: mattrunyon

__mocks__/dh-core.js

@@ -1536,6 +1536,12 @@ class IdeSession extends DeephavenObject {
   getCompletionItems() {
     return Promise.resolve([]);
   }
+  getSignatureHelp() {
+    return Promise.resolve([]);
+  }
+  getHover() {
+    return Promise.resolve({});
+  }
   closeDocument() {}
 
   newTable(columnNames, types, data, userTimeZone) {

packages/components/scss/BaseStyleSheet.scss

@@ -677,10 +677,19 @@ input[type='number']::-webkit-inner-spin-button {
 
 .monaco-editor {
   // Hide the "Loading..." and "No suggestions" message in the suggest widget in monaco to make it feel faster
-  .editor-widget.suggest-widget.message {
+  .editor-widget.suggest-widget.message,
+  .parameter-hints-widget.message {
     display: none;
   }
 
+  .monaco-hover hr {
+    margin-bottom: 4px !important; // Monaco sets this to -4 which causes items below a dividing line to collide w/ the line
+  }
+
+  .parameter-hints-widget {
+    z-index: 30 !important; // Need to make above golden-layout, but below completion item widget at z=40
+  }
+
   .find-widget {
     &.visible {
       // For some reason the height of this is set improperly in 0.18.1

packages/console/src/ConsoleInput.tsx

@@ -14,7 +14,7 @@ import {
   CommandHistoryStorageItem,
   CommandHistoryTable,
 } from './command-history';
-import { MonacoCompletionProvider, MonacoTheme, MonacoUtils } from './monaco';
+import { MonacoProviders, MonacoTheme, MonacoUtils } from './monaco';
 import './ConsoleInput.scss';
 
 const log = Log.module('ConsoleInput');
@@ -513,7 +513,7 @@ export class ConsoleInput extends PureComponent<
             style={{ height: commandEditorHeight }}
           />
           {model && (
-            <MonacoCompletionProvider
+            <MonacoProviders
               model={model}
               language={language}
               session={session}