(Chore) Clear build artefacts script

[vbaranov]

Motivation

To prepare code for deployment to the instance after local testing we need to clear build artefacts. We do it manually now.

Changelog

Enhancements

• ./rel/commands/clear_build.sh bash script has been added, which removes all of those artefacts

• I've updated deployment instruction here: https://forum.poa.network/t/deploying-blockscout-with-terraform/1952#preparing-blockscout.

  • 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 1eb88e1f-16a6-4582-91d6-820fda41a64d

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 7 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.02%) to 82.368%

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Files with Coverage Reduction	New Missed Lines	%
apps/indexer/lib/indexer/block/catchup/bound_interval_supervisor.ex	3	85.19%
apps/indexer/lib/indexer/block/catchup/fetcher.ex	4	69.23%

Totals
Change from base Build e1558521-716b-44a8-8013-18178ccc355a:	-0.02%
Covered Lines:	4438
Relevant Lines:	5388

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💛 - Coveralls

[goodsoft]

What about using git clean -x/-X though?