fix(draw_line): fix the issue where dash_dap equals 1 and cannot display properly when the line is a horizontal line

[lhdjply]

Description of the feature or fix

fix #5029
fix(draw_line): fix the issue where dash_dap equals 1 and cannot display properly when the line is a horizontal line

test code:

void lv_line_dash_dap_test(void)
{
  static lv_point_precise_t line_points[2] = { {50, 50}, {250, 50} };

  lv_obj_t * line1;
  line1 = lv_line_create(lv_screen_active());
  lv_line_set_points(line1, line_points, 2);
  lv_obj_set_style_line_width(line1, 1, LV_PART_MAIN);
  lv_obj_set_style_line_dash_width(line1, 1, LV_PART_MAIN);
  lv_obj_set_style_line_dash_gap(line1, 1, LV_PART_MAIN);
}

before fix

after fix

Notes

• Update the Documentation if needed.
• Add Examples if relevant.
• Add Tests if applicable.
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[kisvegabor]

Very nice, thank you!

Could you add a test with various dash configurations on horizontal and vertical lines too?

[lhdjply]

Done

[W-Mai]

LGTM

[kisvegabor]

Looks good, thank you!