Attempt to avoid specifying BlockHashCount for different mocking::{MockBlock, MockBlockU32, MockBlockU128}

[bkontur]

While doing some migration/rebase I came in to the situation, where I needed to change mocking::MockBlock to mocking::MockBlockU32:

#[derive_impl(frame_system::config_preludes::TestDefaultConfig)]
impl frame_system::Config for TestRuntime {
	type Block = frame_system::mocking::MockBlockU32<TestRuntime>;
	type AccountData = pallet_balances::AccountData<ThisChainBalance>;
}

But actual TestDefaultConfig for frame_system is using ConstU64 for type BlockHashCount = frame_support::traits::ConstU64<10>; here. Because of this, it force me to specify and add override for type BlockHashCount = ConstU32<10>.

This PR tries to fix this with TestBlockHashCount implementation for TestDefaultConfig which supports u32, u64 and u128 as a BlockNumber.

How to simulate error

Just by removing type BlockHashCount = ConstU32<250>; here

:~/parity/olkadot-sdk$ cargo test -p pallet-multisig
   Compiling pallet-multisig v28.0.0 (/home/bparity/parity/aaa/polkadot-sdk/substrate/frame/multisig)
error[E0277]: the trait bound `ConstU64<10>: frame_support::traits::Get<u32>` is not satisfied
   --> substrate/frame/multisig/src/tests.rs:41:1
    |
41  | #[derive_impl(frame_system::config_preludes::TestDefaultConfig)]
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `frame_support::traits::Get<u32>` is not implemented for `ConstU64<10>`
    |
    = help: the following other types implement trait `frame_support::traits::Get<T>`:
              <ConstU64<T> as frame_support::traits::Get<u64>>
              <ConstU64<T> as frame_support::traits::Get<std::option::Option<u64>>>
note: required by a bound in `frame_system::Config::BlockHashCount`
   --> /home/bparity/parity/aaa/polkadot-sdk/substrate/frame/system/src/lib.rs:535:24
    |
535 |         type BlockHashCount: Get<BlockNumberFor<Self>>;
    |                              ^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `Config::BlockHashCount`
    = note: this error originates in the attribute macro `derive_impl` which comes from the expansion of the macro `frame_support::macro_magic::forward_tokens_verbatim` (in Nightly builds, run with -Z macro-backtrace for more info)

For more information about this error, try `rustc --explain E0277`.
error: could not compile `pallet-multisig` (lib test) due to 1 previous error 

For reviewers:

(If there is a better solution, please let me know!)

The first commit contains actual attempt to fix the problem: 3c5499e.
The second commit is just removal of BlockHashCount from all other places where not needed by default.

Closes: #1657

[paritytech-cicd-pr]

The CI pipeline was cancelled due to failure one of the required jobs.
Job name: cargo-clippy
Logs: https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/6262143

[ggwpez]

Smart 🧠

[franciscoaguirre]

Most mocks had 250 for this. I assume it's good anyway, right?

[bkontur]

yes, I think 250 was just random copy&pasted value, looks like there is no test depending on this value, so all test passed and should be ok