What does this PR do?

see: forcedotcom/sfdx-core#1188

QA instructions:
needs to use yarn's resolutions to dedup the mix of nested sfdx-core versions

build

1. checkout this PR
2. add this this resolutions to the pjson:

  "resolutions": {
    "@salesforce/core": "^8.12.1-dev.0"
  },

3. bump to the prerel (this will also install all deps): yarn add @salesforce/core@dev
4. confirm it compiles: yarn compile

agent preview

❗ you need to use Vivek's afdx bug bash org and your specific user
we'll use the local_agent_app app that's already connected to an agent

1. link this plugin branch
2. checkout and link this plugin branch: feat: org login web support for multi auth W-18394868 plugin-auth#1306
3. authenticate with your afdx user the normal way
4. open app manager: sf org open -o afdx-user -p lightning/setup/NavigationMenus/home
5. get app's client id: find local_agent_app -> View -> Manage Consumer Details
6. link the connected app to your afdx user as shown in sf agent preview --help steps.

your afdx auth file should have a new apps object with the linked app oauth creds encrypted.
Run:

sf agent preview --target-org afdx-user --app local-agent-app

and select the local agent, you should be able to start a chat session.

What issues does this PR fix or reference?

@@W-18394868@