Multipurpose front-end part update

[vbaranov]

Closes #2621
Closes #1771
Closes #2641

All visual changes in this PR indicated in parent PR #2637

Motivation

• Missing tooltips for Block Details page
• Inconsistent colours of text in error boxes
• "Jumping" header height on load

Changelog

CSS and Elixir templates updates

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
• If I added/changed/removed ENV var, I should update the list of env vars in https://github.com/poanetwork/blockscout/blob/master/docs/env-variables.md to reflect changes in the table here https://poanetwork.github.io/blockscout/#/env-variables?id=blockscout-env-variables. I've set master in the Version column.
• If I add new indices into DB, I checked, that they don't redundant with PGHero or other tools

[coveralls]

Pull Request Test Coverage Report for Build ecf2133e-6e09-4c15-8ce0-d31c0aad6c6d

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.3%) to 78.91%

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Totals
Change from base Build 652d3b20-36fa-4392-bc78-f6ce5a4b0d96:	0.3%
Covered Lines:	5126
Relevant Lines:	6496

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💛 - Coveralls