Highlight first item in menus upon filtering

[feltech]

If the user moves through the menu then resumes typing, the selectedIndex can end up larger than the contents of the menu. This can cause errors, or at least graphical glitches, and seems odd.

[feltech]

Some pics highlighting the issue

Unfiltered

Then type to filter:

You can see no option is highlighted, and the following exception occurs

vendor.bundle.js:925 Uncaught TypeError: Cannot read property 'rawCompletion' of undefined
    at EventEmitter.Ce._contextMenu.onSelectedItemChanged.subscribe.e (vendor.bundle.js:925)
    at emitOne (events.js:116)
    at EventEmitter.emit (events.js:211)
    at t.Event.dispatch (vendor.bundle.js:632)
    at Object.onSelectedItemChanged (vendor.bundle.js:987)
    at r (vendor.bundle.js:839)
    at vendor.bundle.js:839
    at vendor.bundle.js:824
    at n (vendor.bundle.js:632)
    at Object.filterMenu (vendor.bundle.js:632)

With the fix

[codecov[bot]]

Codecov Report

Merging #2632 into master will increase coverage by 0.05%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2632      +/-   ##
==========================================
+ Coverage   45.33%   45.38%   +0.05%     
==========================================
  Files         361      361              
  Lines       14572    14559      -13     
  Branches     1913     1910       -3     
==========================================
+ Hits         6606     6608       +2     
+ Misses       7741     7725      -16     
- Partials      225      226       +1

Impacted Files	Coverage Δ
browser/src/Services/Menu/MenuReducer.ts	35.89% <ø> (+13.89%)	:arrow_up:
browser/src/Services/Menu/MenuActionCreators.ts	27.77% <ø> (-1.96%)	:arrow_down:
browser/src/Services/ContextMenu/ContextMenu.tsx	18.84% <ø> (+0.26%)	:arrow_up:

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[akinsho]

@feltech I noticed that this PR removes the details code, I'm wondering if this impacts rendering of the documentation section for the autocomplete menu?

[feltech]

I believe the code responsible for processing a completionItem/resolve, which must be where the documentation comes from, was the bit I fixed in #2633. I cannot find any references to the string SET_DETAILED_MENU_ITEM and the related methods that I removed. Grepping the git history, it looks like the final reference to the top-level function updateItem was removed in e2dc9bcbfc11b2d73061deaada865fda26bed9ef as part of a refactor.