Enforce consistent and correct toml formatting (#2518)

Using taplo, fixes all our broken and inconsistent toml formatting and
adds CI to keep them tidy.

If people want we can customise the format rules as described here
https://taplo.tamasfe.dev/configuration/formatter-options.html

@ggwpez, I suggest zepter is used only for checking features are
propagated, and leave formatting for taplo to avoid duplicate work and
conflicts.

TODO
- [x] Use `exclude = [...]` syntax in taplo file to ignore zombienet
tests instead of deleting the dir

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

substrate/frame/staking/runtime-api/Cargo.toml

@@ -18,5 +18,5 @@ sp-api = { version = "4.0.0-dev", default-features = false, path = "../../../pri
 sp-staking = { version = "4.0.0-dev", default-features = false, path = "../../../primitives/staking" }
 
 [features]
-default = [ "std" ]
-std = [ "codec/std", "sp-api/std", "sp-staking/std" ]
+default = ["std"]
+std = ["codec/std", "sp-api/std", "sp-staking/std"]