Expose latest matched version

## Background

When installing a latest version e.g. via

- [`releases.LatestVersion`](https://pkg.go.dev/github.com/hashicorp/hc-install@v0.6.4/releases#LatestVersion)
- [`checkpoint.LatestVersion`](https://pkg.go.dev/github.com/hashicorp/hc-install@v0.6.4/checkpoint#LatestVersion)

or even when discovering existing installation e.g. via [`fs.Version`](https://pkg.go.dev/github.com/hashicorp/hc-install@v0.6.4/fs#Version)

it is currently impossible for the consumer to tell what version was installed after calling `Install`, `Ensure` or `Find` without executing the binary while the library internally already has the knowledge of the matched version.

## Proposal

Expose matched version for the consumer

## Considerations

This may require some breaking changes, e.g. returning a struct `{ ExecPath string, Version *version.Version }` instead of just `string` (exec path) from the various methods like `Install`, `Ensure` and `Find` per https://pkg.go.dev/github.com/hashicorp/hc-install@v0.6.4/src

Start by tracing the Install, Ensure, and Find entry points and the releases.LatestVersion, checkpoint.LatestVersion, and fs.Version paths referenced in the issue. Determine how the matched version can be returned alongside the executable path, then verify that consumers can read it without executing the binary and that the affected API behavior is covered.

Written by the indexing model from the issue text.