Create new tool_version_manager.opt_out config setting

Overview

To aide in a smooth transition away from asdf a new config setting should be used to replace current usages of mise.enabled and asdf.opt_out scattered throughout the codebase.

Now that we have forced users to migrate from asdf in !5198 (merged), and we want to create a golden path to reduce support burden, we should implement a boolean config variable tool_version_manager.opt_out? that allows users to self-manage their tool versions.

See relevant discussion: &19027 (comment 2697612623) !5138 (comment 2707221148) !5138 (comment 2706105202)

Impacted categories

The following categories relate to this issue:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Proposal (optional)

Implement a tool_version_manager.opt_out config variable that initially uses !mise.enabled as the default value.