feat: update the calculation logic of BLS signature threshold

[yutianwu]

Description

This pr will update the calculation logic of BLS signature threshold.

Before we just use len(validators)*2/3 to get the BLS signature threshold. This pr will change the calculation logic of the threshold:

func CeilDiv(x, y int) int {
	if y == 0 {
		return 0
	}
	return (x + y - 1) / y
}

For example, there are total 3 validators.

Before, the threshold of valid signed validator count is 3. If we change the calculation logic, the threshold is 2.

Rationale

To change the calculation logic of BLS signature threshold to be consistent with BSC.

Example

n/a

Changes

Notable changes:

• update the calculation logic of BLS signature threshold