Set compute costs for storage related host functions

[jakmeier]

In #8006 we decided on the compute costs we want to set for flat storage before the next release cut.

We first need to finish the compute costs implementation #8032, then a PR setting the compute costs can be submitted.

At the end, the new costs should be tracked in the NEP-455, but I don't see a reason to do that before we are live on testnet.

[jakmeier]

#8924 sets the costs.
#8938 tracks them in nearcore.
near/NEPs#477 will link it to the NEP

Once the two PRs above are merge, I will close this issue.

[jakmeier]

near/NEPs#477 landed, closing now