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/test-utils/Cargo.toml

@@ -17,5 +17,5 @@ futures = "0.3.16"
 tokio = { version = "1.22.0", features = ["macros", "time"] }
 
 [dev-dependencies]
-trybuild = { version = "1.0.74", features = [ "diff" ] }
+trybuild = { version = "1.0.74", features = ["diff"] }
 sc-service = { path = "../client/service" }