The region_distribution should returns RegionDistribution instead of Result<RegionDistribution>

[WenyXu]

What type of enhancement is this?

Tech debt reduction

What does the enhancement do?

greptimedb/src/common/meta/src/rpc/router.rs

Lines 33 to 46 in b9302e4

	pub fn region_distribution(region_routes: &[RegionRoute]) -> Result<RegionDistribution> {
	let mut regions_id_map = RegionDistribution::new();
	for route in region_routes.iter() {
	if let Some(peer) = route.leader_peer.as_ref() {
	let region_id = route.region.id.region_number();
	regions_id_map.entry(peer.id).or_default().push(region_id);
	}
	}
	for (_, regions) in regions_id_map.iter_mut() {
	// id asc
	regions.sort()
	}
	Ok(regions_id_map)
	}

Here is no reason to return Result<RegionDistribution>, Let's refactor it.

Implementation challenges

No response

[ClSlaid]

I'd like to take a look.

[WenyXu]

I'd like to take a look.

Have fun!