fix(app-shell,app): Send labware files and runtime parameters over USB

[SyntaxColoring]

Overview

Fixes RESC-247 and RQA-2627.

Test Plan

• Following the steps in RESC-247, make sure protocols with custom labware work over USB now.
• Following the steps in RQA-2627, make sure runtime parameters work over USB now.
• Make sure there's no discernable app freeze or hiccup that wasn't there before when you click the "Send" button, especially with a big protocol.
• Make sure other requests (like toggling the lights) are unaffected.
• Make sure requests over Wi-Fi are unaffected.

Changelog

When the Electron rendering process wants to send a USB message, it needs to do so through the Electron main process. This is a problem because some JavaScript types for those messages—Files and Blobs and FormDatas—can't be sent over IPC. We've worked around this for POST /protocols requests by substituting a protocolKey: string in place of these problematic types, in the IPC message. The main process then finds that and reconstructs the Files and FormDatas from it.

That implementation didn't account for labware files external to the protocol (RESC-247), nor did it account for new multipart fields for things like run-time parameters. (RQA-2627).

With this PR, the rendering process slurps all the file contents—protocol and labware—into memory, and then sends them over IPC. We still need to use a substitute structure for the FormData, and the main process still needs to reconstruct all of this back into FormDatas and Files. But the reconstruction code no longer needs to be concerned with application-level ideas like "labware" and "protocols" and where those things live on the filesystem, which is intended to make all of this a bit more robust.

Review requests

See my review comments.

Risk assessment

Medium.

[shlokamin]

nice work, the value.arrayBuffer() conversion was very clever thinking