Finish documenting #[pallet::xxx] macros (paritytech#2638)

Closes paritytech/polkadot-sdk-docs#35

- Moves pallet proc macro docs to `frame_support`
- Adds missing docs
- Revise revise existing docs, adding compiling doctests where
appropriate

---------

Co-authored-by: command-bot <>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

substrate/frame/support/Cargo.toml

@@ -66,6 +66,7 @@ aquamarine = { version = "0.5.0" }
 [dev-dependencies]
 assert_matches = "1.3.0"
 pretty_assertions = "1.2.1"
+sp-timestamp = { path = "../../primitives/timestamp", default-features = false }
 frame-system = { path = "../system" }
 sp-crypto-hashing = { path = "../../primitives/crypto/hashing" }
 
@@ -96,6 +97,7 @@ std = [
 	"sp-std/std",
 	"sp-tracing/std",
 	"sp-weights/std",
+	"sp-timestamp/std"
 ]
 runtime-benchmarks = [
 	"frame-system/runtime-benchmarks",