Caching of address transactions counter, remove query 10_000 rows limit

[vbaranov]

Motivation

1. Address transactions counter query is slow.
2. If there are more than 10_000 transactions, UI displays >= 10000 instead of exact number

Changelog

• Add caching of transactions counter at the address.
• Remove 10_000 query limit.
• A cache is expired if it was updated more than 1 hour ago by default.
• ADDRESS_TRANSACTIONS_CACHE_PERIOD env var is introduced to manage address transactions counter cache update period (in seconds).

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 ab9a7de02c943cfe242f45bd1e3bab0953ebe1e8-PR-3330

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+3.4%) to 74.67%

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Files with Coverage Reduction	New Missed Lines	%
lib/block_scout_web/controllers/address_controller.ex	3	89.29%

Totals
Change from base Build f04fe57690d6aa8d4577521e0fe996bd1bdba4f0:	3.4%
Covered Lines:	1981
Relevant Lines:	2653

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💛 - Coveralls