Deprecate coder_agent.dir and related display_apps

[matifali]

@matifali said in coder/coder-desktop-macos#238:

As of Terraform Provider 2.17.0, a warning is now shown when coder_agent.dir is set to a value other than ~ or $HOME. This does not fix the underlying issue, but it should help prevent users from running into it.

The longer-term plan is to deprecate and remove coder_agent.dir, along with vscode and vscode-insiders in coder_agent.display_apps, since they depend on coder_agent.dir to open a targetted folder. For IDEs, the recommended approach is to use the modules from registry.coder.com, or define an explicit coder_app and use the IDE URL handler to open a folder.