migrations: take()should consume read and write operation weight

[dastansam]

Problem

take() consumes only 1 read worth of weight in single-block-migrations example, while take() is get() + kill(), i.e should be 1 read + 1 write. I think this could mislead developers who follow this example to write their migrations

[paritytech-cicd-pr]

The CI pipeline was cancelled due to failure one of the required jobs.
Job name: test-linux-stable 1/3
Logs: https://gitlab.parity.io/parity/mirrors/polkadot-sdk/-/jobs/6065203

[ggwpez]

I think it depends on the Trie version, but okay. Many chains are still on V0.