Migrating salary pallet to use umbrella crate (#7048)

# Description

Migrating salary pallet to use umbrella crate. It is a follow-up from
https://github.com/paritytech/polkadot-sdk/pull/7025
Why did I create this new branch? 
I did this, so that the unnecessary cargo fmt changes from the previous
branch are discarded and hence opened this new PR.



## Review Notes

This PR migrates pallet-salary to use the umbrella crate.

Added change: Explanation requested for why `TestExternalities` was
replaced by `TestState` as testing_prelude already includes it
`pub use sp_io::TestExternalities as TestState;`


I have also modified the defensive! macro to be compatible with umbrella
crate as it was being used in the salary pallet