New node: Merge by Distance (#2307)

* add `merge_by_distance` node

* remove unneeded features of petgraph

Also re-arrange module slightly since because functions are no longer
async, there was name shadowning with the old arrangement.

* remove region if start or end segment is removed

* remove stuff I ended up not using

* "algos" -> "algorithms"

* Code review pass

---------

Co-authored-by: Keavon Chambers <keavon@keavon.com>

Cargo.toml

@@ -95,6 +95,9 @@ syn = { version = "2.0", default-features = false, features = [
 	"derive",
 ] }
 kurbo = { version = "0.11.0", features = ["serde"] }
+petgraph = { version = "0.7.1", default-features = false, features = [
+	"graphmap",
+] }
 
 [profile.dev]
 opt-level = 1