Change distance evaluation period from Sessions to Blocks

Closes #202 (closed) Closes #207 (closed)

• Create evaluation period in block.
• Update tests.
• Weight accounting
• Upgrade the distance oracle.
• Fix #207 (closed).
• Closes #174 (closed): the worst and simplest estimation equates to one evaluation being 0.0037% of a block's weight, based on the current reference machine. To maintain a reasonable load on the system, it's advisable that the cumulative weight of all evaluations does not surpass 5-10% of a block's capacity. Consequently, setting MAX_EVALUATIONS_PER_SESSION between 1 300 and 2 600 would ensure safe operation.