Calculate staked ratio before insert pools

[saneery]

#1709

Motivation

We need to show a stakes ratio in the interface https://projects.invisionapp.com/share/YPQNPDTW4ZB#/screens/348397338
Stakes ratio is a ratio of a pool stakes amount to the total stakes amount

Changelog

Set the function to calculate the ratio in each pool from the fetched list.

Checklist for your PR

• I added an entry to CHANGELOG.md with this PR
• If I added new functionality, I added tests covering it.
• If I fixed a bug, I added a regression test to prevent the bug from silently reappearing again.
• I checked whether I should update the docs and did so if necessary

[coveralls]

Pull Request Test Coverage Report for Build 6865c179-c013-46de-926d-d52d18f2f01a

• 7 of 7 (100.0%) changed or added relevant lines in 2 files are covered.
• 10 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-0.1%) to 81.125%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/fetcher/token.ex	1	78.57%
apps/indexer/lib/indexer/fetcher/token_balance.ex	2	87.1%
apps/indexer/lib/indexer/block/fetcher.ex	3	87.84%
apps/indexer/lib/indexer/block/catchup/fetcher.ex	4	69.23%

Totals
Change from base Build 17f65b6f-b33a-4dad-b400-ad1d5d8fd47d:	-0.1%
Covered Lines:	4715
Relevant Lines:	5812

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💛 - Coveralls