Memory Leak when using MessageService#showProgress on Backend

[jfaltermeier]

Bug Description:

There is a memory leak when using e.g. MessageService#showProgress on the backend when the Progress is updated many times.

In RpcProtocol new event listeners are added via cancellationToken?.onCancellationRequested(() => this.sendCancel(id)) on each update, but those are not removed again.

This will result in these kind of warnings on the backend log:

2024-01-10T11:24:18.341Z root WARN Possible Emitter memory leak detected. 176 listeners added. Use event.maxListeners to increase the limit (175). MOST frequent listener (1):
2024-01-10T11:24:18.341Z root WARN     at _event.Object.assign.maxListeners (/home/user/git/theia/examples/electron/lib/backend/packages_core_lib_common_index_js-node_modules_vscode-languageserver-types_lib_umd_sync_recursive.js:1430:54)
    at RpcProtocol.sendRequest (/home/user/git/theia/examples/electron/lib/backend/packages_core_lib_common_index_js-node_modules_vscode-languageserver-types_lib_umd_sync_recursive.js:3546:101)
    at /home/user/git/theia/examples/electron/lib/backend/packages_core_lib_common_index_js-node_modules_vscode-languageserver-types_lib_umd_sync_recursive.js:4236:58
    at new Promise (<anonymous>)
    at /home/user/git/theia/examples/electron/lib/backend/packages_core_lib_common_index_js-node_modules_vscode-languageserver-types_lib_umd_sync_recursive.js:4229:64

Steps to Reproduce:

1. Execute this code on the backend:

    @inject(MessageService)
    protected readonly messages: MessageService;

    async init(): Promise<void> {
        const progress = await this.messages.showProgress({ text: 'Progressing...', options: { cancelable: false } });
        for (let i = 1; i <= 1000; i++) {
            progress.report({ message: undefined, work: { done: i, total: 1000 } });
            await wait(50); // import { wait } from '@theia/core/lib/common/promise-util';
        }
    }

(e.g. temporarily add it to packages/git/src/node/init/git-init.ts at the start of the init() method, which already uses the MessageService)

2. Let this run for some time and check that there are multiple logs about the leak.

Additional Information

• Operating System: Ubuntu 22.04
• Theia Version: 1.45.0