Replace window.web3 with window.ethereum

[vbaranov]

Motivation

MetaMask will discontinue injecting window.web3 object to the page https://docs.metamask.io/guide/provider-migration.html#replacing-window-web3. We should handle this change.

Changelog

Replace injected window.web3 object with window.ethereum

Chore:

• refactor write contract functionality

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 59d2f71f0c9c85de9af5563b1d59661d0b21f3b6-PR-3450

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.3%) to 67.266%

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Files with Coverage Reduction	New Missed Lines	%
lib/block_scout_web/controllers/chain/market_history_chart_controller.ex	2	71.43%

Totals
Change from base Build 4e520f7ec3fef1b27f6b123fd18c3723c82ba9e6:	0.3%
Covered Lines:	2057
Relevant Lines:	3058

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💛 - Coveralls