Try to reduce size of completions DTO (#164087)

JS/TS can return a lot of completions. I noticed that just parsing this was taking a bit of time, so I tried to reduce the message size with the following changes:

- Inline the command properties on `ISuggestDataDto`
- Drop the `title` and `tooltip` from the command since we don't use these
- Shorten the delegate command name
- If using an `$ident` command, don't send over the command arguments since the arguments are always `[$ident]`
- Make commit characters a string instead of an array

Here's an example of a dto for a completion item before:

```
{"x":[2,0],"a":"$","b":4,"e":"15","i":0,"k":[".",",",";","("],"m":{"$ident":867,"id":"_vscode_delegate_cmd_l9g7z48t","title":"","arguments":[867]}}
```

And after:

```
{"x":[1,0],"a":"$","b":4,"e":"15","i":0,"k":".,;(","n":11,"o":"__vsl9g7vfno"}
```

For global completions in a JS/TS file, this makes the completion response a little over 40% smaller.

src/vs/workbench/api/browser/mainThreadLanguageFeatures.ts

@@ -472,6 +472,9 @@ export class MainThreadLanguageFeatures extends Disposable implements MainThread
 	private static _inflateSuggestDto(defaultRange: IRange | { insert: IRange; replace: IRange }, data: ISuggestDataDto): languages.CompletionItem {
 
 		const label = data[ISuggestDataDtoField.label];
+		const commandId = data[ISuggestDataDtoField.commandId];
+		const commandIdent = data[ISuggestDataDtoField.commandIdent];
+		const commitChars = data[ISuggestDataDtoField.commitCharacters];
 
 		return {
 			label,
@@ -485,9 +488,14 @@ export class MainThreadLanguageFeatures extends Disposable implements MainThread
 			insertText: data[ISuggestDataDtoField.insertText] ?? (typeof label === 'string' ? label : label.label),
 			range: data[ISuggestDataDtoField.range] ?? defaultRange,
 			insertTextRules: data[ISuggestDataDtoField.insertTextRules],
-			commitCharacters: data[ISuggestDataDtoField.commitCharacters],
+			commitCharacters: commitChars ? Array.from(commitChars) : undefined,
 			additionalTextEdits: data[ISuggestDataDtoField.additionalTextEdits],
-			command: data[ISuggestDataDtoField.command],
+			command: commandId ? {
+				$ident: commandIdent,
+				id: commandId,
+				title: '',
+				arguments: commandIdent ? [commandIdent] : data[ISuggestDataDtoField.commandArguments], // Automatically fill in ident as first argument
+			} as languages.Command : undefined,
 			// not-standard
 			_id: data.x,
 		};

src/vs/workbench/api/common/extHost.protocol.ts

@@ -1547,8 +1547,10 @@ export const enum ISuggestDataDtoField {
 	range = 'j',
 	commitCharacters = 'k',
 	additionalTextEdits = 'l',
-	command = 'm',
-	kindModifier = 'n',
+	kindModifier = 'm',
+	commandIdent = 'n',
+	commandId = 'o',
+	commandArguments = 'p',
 }
 
 export interface ISuggestDataDto {
@@ -1562,10 +1564,13 @@ export interface ISuggestDataDto {
 	[ISuggestDataDtoField.insertText]?: string;
 	[ISuggestDataDtoField.insertTextRules]?: languages.CompletionItemInsertTextRule;
 	[ISuggestDataDtoField.range]?: IRange | { insert: IRange; replace: IRange };
-	[ISuggestDataDtoField.commitCharacters]?: string[];
+	[ISuggestDataDtoField.commitCharacters]?: string;
 	[ISuggestDataDtoField.additionalTextEdits]?: ISingleEditOperation[];
-	[ISuggestDataDtoField.command]?: languages.Command;
 	[ISuggestDataDtoField.kindModifier]?: languages.CompletionItemTag[];
+	// Command
+	[ISuggestDataDtoField.commandIdent]?: number;
+	[ISuggestDataDtoField.commandId]?: string;
+	[ISuggestDataDtoField.commandArguments]?: any[];
 	// not-standard
 	x?: ChainedCacheId;
 }

src/vs/workbench/api/common/extHostCommands.ts

@@ -322,7 +322,7 @@ export const IExtHostCommands = createDecorator<IExtHostCommands>('IExtHostComma
 
 export class CommandsConverter implements extHostTypeConverter.Command.ICommandsConverter {
 
-	readonly delegatingCommandId: string = `_vscode_delegate_cmd_${Date.now().toString(36)}`;
+	readonly delegatingCommandId: string = `__vsc${Date.now().toString(36)}`;
 	private readonly _cache = new Map<number, vscode.Command>();
 	private _cachIdPool = 0;
 

src/vs/workbench/api/common/extHostLanguageFeatures.ts

@@ -1008,6 +1008,7 @@ class CompletionsAdapter {
 			throw Error('DisposableStore is missing...');
 		}
 
+		const command = this._commands.toInternal(item.command, disposables);
 		const result: extHostProtocol.ISuggestDataDto = {
 			//
 			x: id,
@@ -1021,9 +1022,11 @@ class CompletionsAdapter {
 			[extHostProtocol.ISuggestDataDtoField.filterText]: item.filterText !== item.label ? item.filterText : undefined,
 			[extHostProtocol.ISuggestDataDtoField.preselect]: item.preselect || undefined,
 			[extHostProtocol.ISuggestDataDtoField.insertTextRules]: item.keepWhitespace ? languages.CompletionItemInsertTextRule.KeepWhitespace : 0,
-			[extHostProtocol.ISuggestDataDtoField.commitCharacters]: item.commitCharacters,
+			[extHostProtocol.ISuggestDataDtoField.commitCharacters]: item.commitCharacters?.join(''),
 			[extHostProtocol.ISuggestDataDtoField.additionalTextEdits]: item.additionalTextEdits && item.additionalTextEdits.map(typeConvert.TextEdit.from),
-			[extHostProtocol.ISuggestDataDtoField.command]: this._commands.toInternal(item.command, disposables),
+			[extHostProtocol.ISuggestDataDtoField.commandIdent]: command?.$ident,
+			[extHostProtocol.ISuggestDataDtoField.commandId]: command?.id,
+			[extHostProtocol.ISuggestDataDtoField.commandArguments]: command?.$ident ? undefined : command?.arguments, // filled in on main side from $ident
 		};
 
 		// 'insertText'-logic