KeyTipService should dismiss keytips if the first key does not match any keytips

[TimMisiak]

The current behavior is that if you hold down alt for > 0.7 seconds, then press a key that does not match a keytip, the keytip popup remains active, instead of dismissing as office does. This prevents other alt+key based shortcuts from working correctly, since subsequent keystrokes will go to the KeyTipService.

For instance, hold Alt for 3 seconds, then press "5". In word, the keytips will disappear. With fluent, the keytips remain active.

Note that the same isn't true for keytips that are multiple keystrokes long... E.g. if ZS and ZC are both keytip shortcuts and ZQ is not, then pressing Alt (wait 3 seconds), "Z", "Q", the keytips for ZS and ZC will still be active in both office and fluent.

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Environment

• Fluent.Ribbon v8.0.3
• Windows 10 build 21327
• .NET Framework 4.6.1