Make hint labels more like Vimium

[extratype]

For the sake of convenience let hintCharacters be decimals: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9. Suppose there are 21 labels. In current implementation we see

• There are 7 (floor(100-21)/10) short hints: 0 1 2 3 4 5 6
• There are 14 long hints: 70 71 72 ... 83

In this pull request:

• There are 14 long hints: 00 10 20 01 11 21 02 12 22 03 13 23 04 14
• There are 7 short hints: 3 4 5 6 7 8 9

Observations:

• Vimium prefers lower numbers (starting characters) in long hints, not short hints.
• Vimium changes higher decimal places (starting characters) for adjacent items: 00 10 20, not 00 01 02.

I figured this out by just looking labels, not source code, so this implementation may not be exactly same.

By the way there was a typo in HintLabelServiceTEst.cs. I corrected it.

[zsims]

This works great in the cases I tried, subtle but helpful 👍

By the way there was a typo in HintLabelServiceTEst.cs. I corrected it.

Thanks