feat: allow running plugins via path

[patrickjcasey]

This pull request accomplishes 3 main goals:

1. It centralizes the location where all of the LEGACY "plugins" are managed, making it easier in the future to update the codebase to reflect when these features have been updated to use the plugin APIs
2. Adds the ability to run locally built plugins via a provided filepath, allowing for testing plugins, without the need for relying on downloading plugins and their manifests. This is especially useful for running plugins that are actively being developed.
3. It centralizes all of the logic for retrieving plugins in hipcheck/src/plugin/retrieval.rs, both local and remote, and fixes an issue where plugin dependencies were not getting downloaded, nor started.

This pull request also cleans up a couple of small items in the codebase:

• The activity plugin removed mock_engine from its dependencies and added it to its dev-dependencies, as it is only a dependency for testing and should not be running in the context of a normal activity plugin binary
• Cleaned up some log messages to more accurately reflect the current state of the codebase
• Adds some missing SPDX license identifiers
• Fixed a couple of types and minor clippy lints

This pull request also sets the fuzz analysis to be run through the plugin infrastructure. There was a bug with entropy that was only present in the new plugin version of entropy "not enough commits to calculate entropy" was occurring and there is still work on converting the JSON pointer to a span. Once these two issues are resolved, I anticipate it being trivial to convert these analyses to use the plugin infrastructure

[j-lanson]

Looks good, I'll merge when CI passes