chore: update prost, and related crates, to 0.8 (#703)

* chore: update prost, and related crates, to 0.8

Updates prost, prost-derive, prost-build, and prost-types to 0.8.

* Update the last few places

tests/extern_path/my_application/Cargo.toml

@@ -10,8 +10,8 @@ license = "MIT"
 
 [dependencies]
 tonic = { path= "../../../tonic" }
-prost = "0.7"
-prost-types = "0.7"
+prost = "0.8"
+prost-types = "0.8"
 uuid = { package = "uuid1", path= "../uuid" }
 
 [build-dependencies]

tests/extern_path/uuid/Cargo.toml

@@ -9,7 +9,7 @@ license = "MIT"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-prost = "0.7"
+prost = "0.8"
 bytes = "1.0"
 [build-dependencies]
-prost-build = "0.7"
+prost-build = "0.8"