Update to rand:0.8.0

[CAD97]

This is, roughly, intended to be a tracking issue of what's required to cleanly upgrade bevy's tree from rand:0.7 to rand:0.8. Thankfully: not much!

What problem does this solve or what need does it fill?

Update to the latest version of upstream. Randomness is not uncommon in games, and this saves people using the latest version of rand for their game code from having duplicate copies of rand in their dependency tree. This is also currently one of very few out-of-date dependency reported by cargo upgrade^[1].

Describe the solution would you like?

The simple cargo upgrade rand --workspace isn't quite enough to purge rand:0.7 from the tree, as uuid:0.8.1 still uses rand:0.7. uuid:git:master currently uses getrandom:0.1.15 directly, and I've opened uuid-rs/uuid#501 to update to getrandom:0.2 (as used by rand:0.8.0 and already in tree via ahash).

Describe the alternative(s) you've considered?

• Just don't upgrade, and stay on rand:0.7. Drifting behind upstream is definitely not ideal.

Additional context

• Update to getrandom:0.2.0 uuid-rs/uuid#501: PR to update uuid to use getrandom:0.2.0
• Un-breaking-change Uuid::new_v4 uuid-rs/uuid#503: uuid master currently has a breaking change to Uuid::new_v4 to let it return a Result instead of Uuid directly. This feels unnecessary, and would preclude the publishing of uuid as a patch release, so I created this PR to hopefully ease that.

All out-of-date dependencies:

bevy_ecs:
    Upgrading rand v0.7.3 -> v0.8.0
bevy_asset:
    Upgrading crossbeam-channel v0.4.4 -> v0.5.0
    Upgrading notify v5.0.0-pre.2 -> v5.0.0-pre.4
    Upgrading rand v0.7.3 -> v0.8.0
bevy_gltf:
    Upgrading base64 v0.12.3 -> v0.13.0
bevy_wgpu:
    Upgrading crossbeam-channel v0.4.4 -> v0.5.0
    Upgrading crossbeam-utils v0.7.2 -> v0.8.1
bevy:
    Upgrading rand v0.7.3 -> v0.8.0

[CAD97]

The following patch (relying on my patched version of uuid) successfully upgrades the tree cleanly:

diff --git a/Cargo.toml b/Cargo.toml
index 207cd123..62b27eaf 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -77,10 +77,13 @@ bevy_internal = {path = "crates/bevy_internal", version = "0.4.0", default-featu
 
 [dev-dependencies]
 anyhow = "1.0"
-rand = "0.7.3"
+rand = "0.8.0"
 ron = "0.6.2"
 serde = {version = "1", features = ["derive"]}
 
+[patch.crates-io]
+uuid = { git = "https://github.com/CAD97/uuid.git", branch = "for-bevy" }
+
 [[example]]
 name = "hello_world"
 path = "examples/hello_world.rs"
diff --git a/crates/bevy_asset/Cargo.toml b/crates/bevy_asset/Cargo.toml
index e5644853..8807125f 100644
--- a/crates/bevy_asset/Cargo.toml
+++ b/crates/bevy_asset/Cargo.toml
@@ -33,7 +33,7 @@ thiserror = "1.0"
 downcast-rs = "1.2.0"
 notify = { version = "5.0.0-pre.2", optional = true }
 parking_lot = "0.11.0"
-rand = "0.7.3"
+rand = "0.8.0"
 
 [target.'cfg(target_arch = "wasm32")'.dependencies]
 wasm-bindgen = { version = "0.2" }
diff --git a/crates/bevy_ecs/Cargo.toml b/crates/bevy_ecs/Cargo.toml
index e1355f3c..b70e874a 100644
--- a/crates/bevy_ecs/Cargo.toml
+++ b/crates/bevy_ecs/Cargo.toml
@@ -20,7 +20,7 @@ trace = []
 bevy_tasks = { path = "../bevy_tasks", version = "0.4.0" }
 bevy_utils = { path = "../bevy_utils", version = "0.4.0" }
 bevy_ecs_macros = { path = "macros", version = "0.4.0" }
-rand = "0.7.3"
+rand = "0.8.0"
 serde = "1.0"
 thiserror = "1.0"
 fixedbitset = "0.3.1"
diff --git a/crates/bevy_ecs/macros/Cargo.toml b/crates/bevy_ecs/macros/Cargo.toml
index 007751d3..4050c7fa 100644
--- a/crates/bevy_ecs/macros/Cargo.toml
+++ b/crates/bevy_ecs/macros/Cargo.toml
@@ -13,4 +13,4 @@ proc-macro = true
 syn = "1.0"
 quote = "1.0"
 proc-macro2 = "1.0"
-find-crate = "0.6"
\ No newline at end of file
+find-crate = "0.6"
diff --git a/crates/bevy_gilrs/Cargo.toml b/crates/bevy_gilrs/Cargo.toml
index 2480e7f7..50978369 100644
--- a/crates/bevy_gilrs/Cargo.toml
+++ b/crates/bevy_gilrs/Cargo.toml
@@ -17,4 +17,4 @@ bevy_input = { path = "../bevy_input", version = "0.4.0" }
 bevy_utils = { path = "../bevy_utils", version = "0.4.0" }
 
 # other
-gilrs = "0.8.0"
\ No newline at end of file
+gilrs = "0.8.0"