Entity selector keyboard control

[cconard96]

Checklist before requesting a review

• I have read the CONTRIBUTING document.
• I have performed a self-review of my code.

Description

Fixes glpi-project/roadmap#308

Entity Selector now auto-focuses the search input when shown.
Keyboard controls (mostly standard):

• Up/Down - Move to previous/next visible node (including children)
• Left - If a leaf node, moves to the parent. If a parent node, collapses the node and moves to the next parent.
• Right - If a parent node, expands the node.
• Enter - Selects the current entity
• Enter + Ctrl/Command - Selects the current entity and its children