[HTML Report] Reduce report load time by deferring collapsed section parsing

[hotbees]

HTML reports are real heavy on HTML. A significant portion of page load time on reports (very noticably on larger ones) is spent parsing HTML and building the DOM. This can result in larger reports like the full-raid sim stack taking several seconds (perhaps an understatement depending on hardware) to fully load and be usable.

Defer section parsing

By wrapping heavy per-actor subsections in <script type="text/x-deferred-html"> blocks, we can have the browser skip parsing these sections upfront, and we can instead later inject this unparsed HTML into the DOM with a bit of JS once the section is expanded.

There's still a lot going on in an HTML report, so this doesn't completely eliminate the problem, but it does give us a report with a much faster time-to-interactive by avoiding having the browser do heavy parsing and DOM construction inside actor sections that may never be opened.

Profiling

MID1_Raid.simc report, average of 3 runs each (Chrome DevTools traces):

Metric	Before	After	Speedup
ParseHTML	1139 ms	554 ms	2.1x
DOMContentLoaded	1789 ms	705 ms	2.5x
Load	1828 ms	707 ms	2.6x
Time to Interactive	2940 ms	1068 ms	2.8x

Where Time to Interactive is when the main thread stops being tied up by long tasks, i.e. when interactions respond without lag (~1.9 s sooner here).

Measurements were done in a Chrome incognito mode window without any extensions loaded. Certain extensions can compound on the load time and make the differences even more stark. For example, doing the same measurements (single run) in my regular browser window gives a DCL before/after of 9,926 ms / 990 ms (10x) and TTI 16,897 ms / 2,266 ms (7.5x).

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Deferred sections: Abilities, Buffs, Procs/Uptimes/Benefits, Resources, Action Priority List, Statistics & Data Analysis, Stats, Gear, Profile, Talents (multi-actor reports only), Parsed Player Effects - each builds on first expand.

Other low-hanging fruit

Additionally, this addresses a couple low-hanging fruit which improve the feel of (esp. larger) reports as the page loads:

1. Emit the raid dps chart in HTML generation. Currently, the raid dps chart isn't loaded until document ready. This is often the star of the show on large sim stacks and having it visible ASAP rather than deferring it is an easy W for usability.

2. Emit the section-open / grouped-first / grouped-last classes in HTML on impactful sections:

   • section-open for the default-open sections (raid summary and profile sets). These are already marked by "toggle open" classes, but the section-open class which visually separates a given section from the rest isn't applied until validate_section() runs at document ready, causing a slightly jarring layout shift as the sections snap apart.
   • grouped-first for hotfixes and grouped-last for the table of contents apply the corner rounding to the separated group above the raid summary. Fairly minor but this styling also currently gets deferred until document ready and this specific group is visible in the top of the page, so it makes sense to apply them early as a mostly-correct first approximation.

For consistency, I also put section-open on the main player for single actor reports since it's also open by default and there's a noticable snap apart there.