New IC3: extract property driver helpers

[kroening]

Summary:

• extract property-literal construction into a helper
• extract per-property solver invocation into a helper
• extract result mapping so the top-level engine loop is easier to scan

Verification:

• make -C src/new-ic3 CXX='ccache clang++' CCACHE_DIR=/tmp/ccache-hw
• make -C src/ebmc CXX='ccache clang++' CCACHE_DIR=/tmp/ccache-hw
• ./src/ebmc/ebmc regression/ebmc/new-ic3/proved1.sv --new-ic3 --property main.p0
• ./src/ebmc/ebmc regression/ebmc/new-ic3/refuted1.sv --new-ic3 --top main
• ./src/ebmc/ebmc regression/ebmc/new-ic3/cover1.sv --new-ic3 --top main