[Tooling] Automate GitHub release publishing for beta builds

[iangmaia]

Reference: pdnsEh-24G-p2

• Android counterpart PR: [Tooling] Automate GitHub release publishing for beta builds simplenote-android#1725
• ReleasesV2 PR: https://github.a8c.com/Automattic/wpcom/pull/176219

Description

This PR updates the upload_to_app_store_connect lane to automate the publishing of beta builds:

• Beta releases: Set as prerelease=true and draft=false to publish immediately as a pre-release
• Final releases: Set as prerelease=false and draft=true to create as a draft until we get Apple approval and can publish it

Testing Steps

We'll be able to fully verify this works as expected during the next Simplenote iOS release cycle.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Simplenote Prototype Build by scanning the QR code below to install the corresponding build.

	App Name	Simplenote Prototype Build
	Build Number	pr1703-82cbaf3-019571b1-4ba3-4113-8d2e-0de0a3d4c31f
	Version	4.55
	Bundle ID	com.codality.NotationalFlow.Alpha
	Commit	82cbaf3
	App Center Build	Simplenote - Installable Builds #431

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[dangermattic]

	1 Warning
⚠️	PR is not assigned to a milestone.

Generated by 🚫 Danger