SYSML2_ — Graphical BNF production proxy should be contextualized

proxy refers to proxy-label should be sq-proxy-label
The BNF attempted to reuse the proxy graphics and productions across all three contexts where a proxy may appear (lifeline, ports, and parameters), but all these need to be replaced by proxy graphics specific to each context, including connector line segments above and below, or left and right, in each specific graphic context where a proxy dot may appear.

Graphical BNF production proxy should be contextualized

Proxy nodes are currently specified in clause 8.2.3.9 without a context and reused later in clauses 8.2.3.12 and 8.2.3.16.
There is a need to specify proxy "in context" nodes similar to ports and parameters, that support the parts and action edge context with the correct orientation.