fix(autocomplete): input focus behavior on value change

[katebatura]

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Short description of what this resolves:

Closes #2401

Focus behavior when a value is set to the input bound to an Autocomplete:

• handled by writeValue() don't focus the input.
• because of autocomplete interactions (option mouse/keyboard select) the input is on focus.

BREAKING CHANGE:
Removed focusInputOnValueChange from NbAutocompleteDirective. Now autocomplete focuses input only when value is selected by option click or keyboard selection.

[yggg]

Shouldn't we also focus input when selecting option by enter (handleInputValueUpdate call from the subscribeOnOverlayKeys method)?