Force Canvas source for Text rendering (accelerated Canvas bug in Cairo)

[wouterlucas]

Lightning 2 has a forceTxCanvasSource setting to deal with Canvas Text rendering out in blocks on WPEWebKit devices. We will need a similar solution in L3.

Apparently there is a Cairo bug with text, which most WPEWebKit installs rely on to draw Canvas. If the Canvas text is larger then a certain threshold the text will be rendered as blocks. For example:

This is due to a bug in Cairo, newer WPEWebKit's will not have this issue if they switch to the Skia backend. There is a workaround being suggested to raise the threshold from 1/4th to 1/2th of the view port when to accelerate Canvas, per WPEWebkit Issue:
WebPlatformForEmbedded/WPEWebKit#1399

We'll need a similar stopgap solution in Lightning 3 as this might take a bit to roll out everywhere.

Original issue in L2:
rdkcentral/Lightning#363

Introduction of forceTxCanvasSource in L2:
rdkcentral/Lightning#364
rdkcentral/Lightning#393

Current implementation:
https://github.com/lightning-js/renderer/blob/main/src/core/text-rendering/renderers/CanvasTextRenderer.ts#L358