Update instructions for auto-approval of tools and terminal commands

[ntrogh]

In 1.104, the instructions and flow for auto-approving tools and terminal commands are changing. We're also introducing a policy for terminal approval.

Update the following docs accordingly in vnext branch for the upcoming release.

• https://code.visualstudio.com/docs/copilot/chat/chat-agent-mode#_manage-tool-approvals
• https://code.visualstudio.com/docs/setup/enterprise#_centrally-manage-vs-code-settings