[FEAT] Provide an option to ignore BPMN LabelStyles

[tbouffard]

Is your feature request related to a problem? Please describe.

In August 2020 in #555 and in November 2020 in #869, we tried to have style options to ignore the font defined in the LabelStyles configuration.
This allowed to force the font to be consistent with the sketchy BPMN theme.

Sometimes, the LabelStyles are not consistent in a diagram: some shapes define a font, others don't. The rendering is then not consistent.

Describe the solution you'd like

Pass an option at library initialization (like proposed in #1993) or at load time (with a new option in LoadOptions) to ignore the LabelStyles configuration defined in the BPMN diagram.
Decide if we ignore only the font or all label styles configuration.
Important: the name of the options have been decided in #2659