Remove element-cache

[t9md]

Description of the Change

Because I've got no response for #106.
Element-cache introduce unfix-able BUG.
And IMO no longer having real perf-gain by this feature now.
I will proceed to send this PR to remove element-cache I believe it should.

• Item element cache mechanism is implemented in Cache element items on creation #94.
• Humanized keystroke cache is implemented in Cache readable item keystroke representations #97.

I'll explain some history/background for this feature. Pls ignore if you already agree to remove this feature.

Before render-on-visible PR

When #94 and #97 is implemented render-on-visible PR #101 had not yet be merged.

At that time command-palette did

• When launch, render all items even if it's not visible in viewport(e.g. render 700 item elements when vim-mode-plus installed)
  • This make launch of command-pallette noticeably slow.
• select-next/select-previous always re-render full item.

Because of such frequent full-item re-render behavior, element-cache introduced noticeable perf improvement for subsequent launch of command-palette:toggle(still very first launch was slow).

After render-on-visible PR

At that time command-palette does

• When launch, just render 10 items regardless of actual item count. And render other items on visible timing.
  • So number of total registered command no longer have big impact for item rendering.
  • This make command-palette:toggle launch faster at very first invocation.
• select-next/select-previous just render old and new selected item(two items).

Like this, chance of over hundreds full-item rendering is no longer happen.
So perf-gain where element-cache can introduce is no longer noticeable.

Here is Me and @jarle(implemented element-cache)'s discussion about this

#97 (comment)
#97 (comment)

Element cache is not fit in etch's VDOM diff based rendering

Element cache's bad impact was fixed in #105.
But still we can hit BUG introduced by element-cache as I described in #106.
And which is not controllable by command-palette side since it's depend on which pkg/command name to be used by user.
If commands start a char, it likely to become top of list, so more chance to hit this BUG.

Alternate Designs

I evaluated to keep seem-to-harmless humanized keystroke cache feature.
But I could not say noticeable diff so removed too.

Benefits

No unfixable exception.

Possible Drawbacks

None

Applicable Issues

[daviwil]

Looks good, thanks @t9md!

[t9md]

Thanks.

Off topic.
Can you check #108? Which is more important than this PR, affecting every launch of palette in current beta.