[time-picker] Introduce format property

[yuriy-fix]

Introduce a new property / attribute, i.e. format, to set format with predefined constraints, like hh:mm.ss

[rolfsmeds]

This should probably be aligned with DatePicker, which (since V22) supports one format string for both parsing and (display) formatting, and optional additional format strings for parsing.

[sissbruecker]

Closing in favor of: vaadin/flow-components#2831