* text box: rework text box to use less memory
* text box: optimize lines iteration
* text box: fix back scrolling
* text box: add end focus support
* text box: allocate index buffer on stack instead of heap
* text box: fix index decrement
* apps: add text box debug app
* debug: rework text box view app with view stack
* debug app: rename text_box_test app to text_box_element_test
* text box: rework text box module
* debug: update text box view test
* text box: fix end focus initial offset
* debug: fix memory leak in text box view test app
Co-authored-by: あく <alleteam@gmail.com>
Co-authored-by: hedger <hedger@users.noreply.github.com>
