Fix Staking DApp first loading

[varasev]

Motivation

Currently, when loading the Staking DApp it makes an async call (request) to load items several times because of duplicated firstPageLoad calls in apps/block_scout_web/assets/js/lib/async_listing_load.js. This PR adds an ability to not call the firstPageLoad when we don't need it. It can be turned on by a separate HTML attribute data-no-first-loading in a div with data-async-load attr for any module. This PR turns this on only for the staking module.

Without this PR we observe the pool list disappearing when using any tab within the Staking DApp UI because of the excess calls. They visually disappear until the next block arrives.

I think this also relates to other modules but propose to optimize it in separate PRs by removing excess requests when using the async_listing_load.js.

Checklist for your Pull Request (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 by submitting a PR to https://github.com/blockscout/docs
• If I added/changed/removed ENV var, I submitted a PR to https://github.com/blockscout/docs to update the list of env vars at https://github.com/blockscout/docs/blob/master/for-developers/information-and-settings/env-variables.md and I updated the version to master in the Version column. Changes will be reflected in this table: https://docs.blockscout.com/for-developers/information-and-settings/env-variables.
• If I add new indices into DB, I checked, that they are not redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build 862f76fc3f3608be946e4a2c79298e429779e61d-PR-3505

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-1.09%) to 67.023%

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Totals
Change from base Build 2b305fdd7decd0ad621aa1cd31aabb55451c0418:	-1.09%
Covered Lines:	2071
Relevant Lines:	3090

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💛 - Coveralls