Replace uint16_t with size_t for rule/blueprint routing to eliminate narrowing warnings

[boulabiar]

• routing: use size_t for rule/blueprint indices; remove narrowing;

• Replace uint16_t-based indices with size_t to avoid narrowing warnings.
• include/crow/common.h
  • routing_handle_result
    • rule_index → size_t (was uint16_t)
    • blueprint_indices → std::vector<size_t> (was std::vector<uint16_t>)
    • Constructors updated to take size_t and std::vector<size_t>
• include/crow/routing.h
  • Constants
    • INVALID_BP_ID → constexpr size_t INVALID_BP_ID{SIZE_MAX} (was uint16_t)
    • RULE_SPECIAL_REDIRECT_SLASH → constexpr size_t = 1 (was const int)
  • Trie::Node
    • rule_index → size_t (was uint16_t)
    • blueprint_index → size_t (was uint16_t)
  • Trie::find
    • Signature: pos → size_t; blueprints → std::vector<size_t>*
    • Locals: MT → std::vector<size_t>, found → size_t, found_BP → std::vector<size_t>
  • Trie::add
    • Signature: rule_index → size_t; blueprint_index → size_t
  • Router wiring
    • internal_add_rule_object overload BP_index → const size_t&
    • get_found_bp signature → std::vector<size_t>, index → size_t
    • bpi locals → std::vector<size_t>
    • Default routing_handle_result construction uses std::vector<size_t>()
    • rule_index locals → size_t

[boulabiar]

A stress test creating thousands of routes may be useful to see whether this reduced performance due to cache misses from the use of a bigger strcuture (size_t == 2x uint16_t)

[gittiver]

Well, that is done on startup normally, so it should have no influence when all rules are setup and requests are handled.
But, well, testing is always a good idea.