[WIP] feat: add initial vaadin-month-picker component implementation

[web-padawan]

Description

This is a prototype PR adding an MVP of vaadin-month-picker.

The component itself is a significant rewrite of the vcf-month-picker with some adjustments:

• Instead of wrapping vaadin-text-field, the component uses mixins e.g. InputControlMixin etc
• The vaadin-month-picker-overlay is rewritten to use native popover to align with other components
• The vaadin-month-picker-overlay-content uses slotted vaadin-month-picker-button elements
• The component is updated to use LumoInjectionMixin with some small tweaks to the Lumo theme
• Added I18nMixin, modified the default i18n structure, added prevYear and nextYear strings
• Modified checkValidity() and some other logic around detecting and dispatching change event
• Removed getters e.g. formattedValue, yearMonth and inputValue (might add later if needed)

Type of change

• Prototype

[sonarqubecloud]

Quality Gate failed

Failed conditions
3.6% Duplication on New Code (required ≤ 3%)
C Reliability Rating on New Code (required ≥ A)

See analysis details on SonarQube Cloud

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