Add Heap parameter to Dijkstra and Prim algorithms

[pratzl]

Add use_default_heap and use_indexed_dary_heap tag types to all Dijkstra and Prim function signatures:

• dijkstra_shortest_paths (single- and multi-source)
• dijkstra_shortest_distances (single- and multi-source)
• prim (mst.hpp)

Add dijkstra_heap_tags.hpp snippet with the two tag struct definitions.

Update algorithms.tex Dijkstra and Prim sections:

• Add lstinputlisting of heap-selector tag definitions (texcl=false to avoid LaTeX interpreting underscores in // comments)
• Describe both tags with usage guidance and E/V ratio recommendations
• Update \complexity to reflect per-tag time/space bounds
• Update \remarks to document the Heap parameter and arity guidance