sum_tree: Replace rayon with futures (#41586)

Release Notes:

- N/A *or* Added/Fixed/Improved ...

Co-authored by: Kate <kate@zed.dev>

Cargo.lock

@@ -12711,6 +12711,12 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5da3b0203fd7ee5720aa0b5e790b591aa5d3f41c3ed2c34a3a393382198af2f7"
 
+[[package]]
+name = "pollster"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2f3a9f18d041e6d0e102a0a46750538147e5e8992d3b4873aaafee2520b00ce3"
+
 [[package]]
 name = "portable-atomic"
 version = "1.11.1"
@@ -12759,7 +12765,7 @@ dependencies = [
  "log",
  "parking_lot",
  "pin-project",
- "pollster",
+ "pollster 0.2.5",
  "static_assertions",
  "thiserror 1.0.69",
 ]
@@ -14311,7 +14317,6 @@ dependencies = [
  "gpui",
  "log",
  "rand 0.9.2",
- "rayon",
  "sum_tree",
  "unicode-segmentation",
  "util",
@@ -16237,6 +16242,7 @@ checksum = "2b2231b7c3057d5e4ad0156fb3dc807d900806020c5ffa3ee6ff2c8c76fb8520"
 name = "streaming_diff"
 version = "0.1.0"
 dependencies = [
+ "gpui",
  "ordered-float 2.10.1",
  "rand 0.9.2",
  "rope",
@@ -16355,9 +16361,11 @@ version = "0.1.0"
 dependencies = [
  "arrayvec",
  "ctor",
+ "futures 0.3.31",
+ "itertools 0.14.0",
  "log",
+ "pollster 0.4.0",
  "rand 0.9.2",
- "rayon",
  "zlog",
 ]