Enable vault linear distribution following the withepaper tokenomics description.

Vault block rewards are ready to be activated, according to the Interlay tokenomics: 30% of 4 year supply (i.e., 300 million INTR), emitted as follows:

• 40% in the first year (120 million INTR)
• 30% in the second year (90 million INTR)
• 20% in the third year (60 million INTR)
• 10% in the fourth year (30 million INTR)

See details here https://interlay.subsquare.io/post/6