Improve Enqueued Assets report in Site Health

[mxbclang]

The current Site Health reports for the Enqueued Assets module, introduced in #25, do not include actionable information for users about how to address a site loading too many enqueued assets. As noted by @felixarntz here:

We also need to think about how to make this warning more actionable, e.g. at a minimum tell users which plugins or themes are responsible for enqueuing the majority of assets etc.

Suggestions for changes (in progress) are below.

Enqueued scripts

If acceptable

Current description: The amount of [#] enqueued scripts (size: [size]) is acceptable.

New description:

If not acceptable

Current description: Your website enqueues [#] scripts (size: [size]). Try to reduce the number or to concatenate them.

More info about performance optimization

Clean Test Cache

New description:

Enqueued styles

If acceptable

Current description: The amount of [#] enqueued styles (size: [size]) is acceptable.

New description:

If not acceptable

Current description: Your website enqueues [#] styles (size: [size]). Try to reduce the number or to concatenate them.

More info about performance optimization

Clean Test Cache

[felixarntz]

@bethanylang The recommendation "Try to reduce the number or to concatenate them." would only address the number of files problem, not the overall amount of JS/CSS problem. So I think that would only be the first half of the solution. We also need some at least high-level advice for when it's overall too much JS/CSS - which is obviously harder to resolve because concatenating won't reduce that, you would actually need to optimize the code as a developer, or identify which parts of the JS/CSS is maybe not critical (or from a non-critical plugin) so that you can remove it.

I think we should also show only the advice that applies, based on whether the amount of JS/CSS exceeds the threshold or whether the number of files of JS/CSS exceeds the threshold. Or if both, we would show both. But the main point here would be to also provide a recommendation for the first scenario.