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/client/executor/Cargo.toml

@@ -55,7 +55,7 @@ name = "bench"
 harness = false
 
 [features]
-default = [ "std" ]
+default = ["std"]
 # This crate does not have `no_std` support, we just require this for tests
 std = [
 	"sc-runtime-test/std",