[MOL-22548] Add optional addon props for LocalNav & Drawer

[jhyeep]

Type of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing apis or functionality to change)
• Documentation (change to documentation, comments or API descriptions)
• Tests (improvements to unit tests or E2E tests)
• Other (technical improvements, refactoring, or changes that don't fall into the above categories)

Description of changes

• MOL-22548
• LocalNav
• Drawer

Drawer — customCallToAction

• New prop customCallToAction?: JSX.Element on DrawerProps, rendered in the
  header alongside the heading.
• Wide drawer: CTA sits inline to the right of the heading (heading truncates
  with an ellipsis).
• Narrow drawer (useMaxWidthMediaQuery("sm")): CTA wraps below the heading,
  indented to line up with the title text, buttons flushed left.

LocalNav — titleAddon

• New prop titleAddon?: TitleAddonProps on the shared LocalNavItemProps
  (both LocalNavMenu and LocalNavDropdown).
• Own type with two slots: { left?: JSX.Element; right?: JSX.Element } — both
  usable at once. left renders before the title; right renders after and is
  flushed to the far right (margin-left: auto).
• Wrapping titles: left addon (and the selected-item tick in the dropdown)
  stay aligned to the first line; right addon stays vertically centred. Handled
  natively by the component.
• Ignored when a custom renderItem is supplied (caller owns layout).

Checklist

• Changes follow the project guidelines in CONTRIBUTING.md and CONVENTIONS.md
• Looks good on mobile and tablet
• Updated documentation
• Added/updated unit tests
• Added/updated E2E tests

Screenshots

Drawer

LocalNav