feat: deprecate ipcRenderer.sendTo()

[miniak]

Description of Change

It's not possible to do proper validation of the sender in the renderer receiving the IPC as only the senderId is available, but not the senderFrame. This is a concern when nodeIntegrationInSubFrames is enabled in the originating renderer. The API can also only send the IPC to the main frame in the receiver.

This API is redundant as it can be easily replaced by sharing a MessageChannel between the two renderers. The main process can validate the senderFrame before forwarding the MessagePort to the other renderer. Performance should also be better as a direct mojo connection is established between the renderers, instead of the IPC being proxied by the main process.

This API does not seem to be used much: https://github.com/search?q=ipcRenderer.sendTo&type=code
Related to #38868

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• tests are changed or added
• relevant documentation, tutorials, templates and examples are changed or added
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: The ipcRenderer.sendTo() API has been deprecated in favor of sharing a MessageChannel between two renderers.

[zcbenz]

API LGTM

[codebytere]

API LGTM

[dsanders11]

Let's also add _Deprecated_ to the end of this line in the docs:

electron/docs/api/ipc-renderer.md

Line 195 in 4ab0a5a

### `ipcRenderer.sendTo(webContentsId, channel, ...args)`

[miniak]

Let's also add _Deprecated_ to the end of this line in the docs:

electron/docs/api/ipc-renderer.md

Line 195 in 4ab0a5a

### `ipcRenderer.sendTo(webContentsId, channel, ...args)`

@dsanders11 done

[release-clerk]

Release Notes Persisted

The ipcRenderer.sendTo() API has been deprecated in favor of sharing a MessageChannel between two renderers.