Setting to control "transparent init" behavior

Executing various skaffold subcommands (`skaffold run`, etc.) in the wrong directory will invoke the "transparent init" behavior. (proposed in #1273, implemented in #5186) This feature can be useful when invoked within a project directory, but also extremely undesirable when not. For example, if a user with a large home directory structure accidentally pastes `skaffold run` into their terminal from the base of their home directory (wrong terminal, mistaken working directory, etc.), this will trigger an init scan of their home directory that is unexpected and in some cases time consuming. This init can sometimes be difficult to break out of with ctrl-c.

It is a given that software need not adhere to the [principle of least astonishment](https://en.wikipedia.org/wiki/Principle_of_least_astonishment) to the point of inconvenience, but ignoring it should not *result in* inconvenience or potentially disruptive behaviors by default.

### Expected behavior

`skaffold init` should not be an unrequested behavior. Some suggestions:

- Add an option that can be placed in the global config that enables transparent init without prompting. (the current behavior) I'm going to refer to this option as `transparent-init` for now, since it is consistent with the name used internally to refer to this feature.
- Consider multiple values for the `transparent-init` setting:
- `yes`: The current default. Immediately invoke `skaffold init` with no prompting. It should be the default when a terminal is not present, but non-interactive tools should be able to request `no` via the commandline option if it is undesirable. **This would maintain backward compatibility with unattended execution that relies on the current default**, such as with scripts or VS Code plugins.
- `no`: Fail normally with no prompting. This was the behavior prior to #5186 if I'm not mistaken.
- `ask`: A new mode that I am proposing below. It should be the default when a terminal is present.
- `ask` mode would be new and is intended to be a compromise between the two previous behaviors.
- It should only be available when a terminal is detected. If a terminal is not connected, `ask` should be treated as `yes`.
- The user is prompted for whether they wish to run `skaffold init`, and a message should be printed that drives the user's attention to the existence of the new `transparent-init` option that makes this prompt go away. (by setting the mode to `yes` or `no`)

There is a lot of impact to consider with this change, and the above proposal is intended to be flexible while minimizing the impact to external dependencies. Please offer feedback and alternatives.

### Information

- Skaffold version: v2.3.0
- Operating system: Ubuntu 20.04.4
- Installed via: skaffold.dev
- Contents of skaffold.yaml: N/A

### Steps to reproduce the behavior

1. Change working directory to any path on a filesystem that incorporates many nested subdirectories with a large file count.
2. Execute any subcommand of `skaffold` that redirects the user into `skaffold init` if a configuration file is not found, such as `skaffold run`.
3. Suffer, if you're unlucky. :)