Print a line mentioning what plugin/version is currently being installed

### Is your feature request related to a problem? Please describe

If you run `asdf install` on a project with multiple tools defined in `.tool-versions` you get hit with a wall of output from the various tools being installed/built/etc. This is fine, but if an error occurs with one of those (in an automated process, perhaps - like CI) it can be quite difficult to figure out exactly where the error has occurred.

On the other hand, if those tools are already installed, `asdf` outputs a line similar to `package 1.2.3 is already installed`.

It would be good to add `installing package 1.2.3` into the "wall of output" so somebody trying to pick through the history of a failing bulk install has at least a breadcrumb to go on.

### Describe the proposed solution

when installing a plugin, the following outputs:

`package 1.2.3 is downloading`
`package 1.2.3 is installing`

or similar

### Describe similar `asdf` features and why they are not sufficient

running `asdf install` on already installed tools already outputs a readable line, but this isn't helpful in automated jobs

### Describe other workarounds you've considered

I considered breaking up our install into separate invocations of `asdf`, but the tool already has the ability to process the `.tool-versions` file and install any missing tools.

Start by running `asdf install` with multiple tools listed in `.tool-versions` and trace where plugin installation output is produced. Done means bulk installs print a readable plugin and version breadcrumb, such as downloading or installing, so failures can be matched to the tool being processed.

Written by the indexing model from the issue text.