Fix text texture RTL propagation

[elsassph]

Element's texture instance doesn't receive the RTL flag in some scenarios due to the "side-effects optimisation" in ElementCore, this causes text alignment to not be automatically mirrored (e.g. left alignment becoming right).

Note:

• the bug doesn't happen with the classic component templating approach, only when manually creating elements,
• test file was reformatted, the main addition is the new it("Should propagate flag after attachment" new last case, plus a few assertions that labels were rendered with the right direction flag.

In this screenshot, before the bug, the "Dynamic attachment" label would remain left-aligned instead of being right aligned with the blue box as we can see here:

[amurillo-wm]

Tested locally and text is mirrored properly

[michielvandergeest]

LGTM!