Update tree key value to 'select-tree-key' in SelectTree class

[CodeWithDennis]

This pull request updates the setUp method in the SelectTree component to use a consistent and descriptive key for the tree instead of a randomly generated one.

Key update:

• src/SelectTree.php: Replaced the dynamic treeKey value ('treeKey-' . rand()) with a static and more descriptive key ('select-tree-key') in the setUp method. This ensures consistency and predictability in the tree key assignment.

This should fix the field flickering

[buzkall]

This change breaks the option to change the relationship query with $modifyQueryUsing using a $get variable

In v 3.1.54 this code updates the options in the selectTree when the select 'module' is updated and has live() enabled

->relationship(
    'category',
    'name',
    'parent_code',
    fn($query, Get $get) => $query->when($get('module'), fn($query) => $query->module($get('module'))),
)

in v 3.1.55 the options aren't updated

[CodeWithDennis]

@buzkall Thanks for reporting! I have reverted this change.