phlib: Implement horizontal scrolling via Shift + Mousewheel

[NotEnsoul]

Summary

This pull request implements horizontal scrolling when holding the Shift key while using the mouse wheel across table, tree, and list controls in the application.

• TreeNew Control (phlib/treenew.c):

  • Checks for MK_SHIFT flag during WM_MOUSEWHEEL handling.
  • When Shift is held and horizontal scroll is visible (Context->HScrollVisible), routes mouse wheel turns to PhTnpProcessMouseHWheel with inverted delta (-Distance), enabling smooth horizontal scrolling.
  • Falls back gracefully to vertical scrolling if horizontal scrolling is unavailable or Shift is not held.
  • Automatically enables Shift + mousewheel horizontal scrolling across all process, service, network, handle, module, thread, memory, disk, and plugin tables.

• Extended ListView (phlib/extlv.c):

  • Intercepts WM_MOUSEWHEEL in PhpExtendedListViewWndProc when MK_SHIFT is active.
  • Calculates scroll distance using SPI_GETWHEELSCROLLCHARS and dispatches WM_HSCROLL (SB_LINERIGHT / SB_LINELEFT) messages for horizontal scrolling.

• Theme Engine (phlib/theme.c):

  • Added WM_HSCROLL and WM_MOUSEHWHEEL invalidation support to PhpThemeWindowACLUISubclassProc.

Resolves

• FR: Scroll horizontally on Shift+MouseWheel #2667