Update ADO pipelines in each release branch to target the correct VS toolchain

[jonthysell]

Summary

We need to make sure that each release branch runs CI on the appropriate VS toolchain.

This captures:

• [ ] Switching the pipelines in main/latest to use the new VS2022 images/pools/agents
• [ ] Setting up the old VS 2019 agents/images on-demand
• [ ] Switching all prior supported stable releases to using the old VS2019 images/pools/agents

Motivation

RNW needs to start building on VS 2022, so we need to start running that latest CI on VS 2022, but we also need to make sure that the older supported branches still run VS 2019.

Basic Example

No response

Open Questions

No response

[jonthysell]

We should start clarifying our VS 2019 - 2022 migration story.

[jonthysell]

This is getting closer, leaving on 0.69 for now but this may move to 0.70.

[jonthysell]

0.69 is getting too close for a sudden toolchain change, moving to 0.70.

[jonthysell]

Depends on #8740 and #8750

[jonthysell]

This is a priority for 0.71.

[jonthysell]

We've decided to leave the existing branches' pipelines using the rnw-img-node16 image, targeting VS 2019, and create a new whole new image for branches needing VS 2022 going forward.