IGV: refine 'Simplify graph' filter

The 'Simplify graph' filter aims at raising the level of abstraction and improving the layout of the presented graph by e.g. combining projections into their parent nodes, inlining constants into their users, etc. These transformations have great potential but are not fully exploited in their current form. This RFE proposes extending the current set of simplifications applied by the filter, for example by:
- combining Bool nodes into their parents and showing only their tested condition,
- compressing the text displayed in combined and inlined nodes to improve the layout quality (which is severely degraded in the presence of wide nodes),
- combining Mach projections and other nodes such as conversions, and
- inlining further nodes such as ThreadLocal and MachTemp.