feat: exclude empty contracts by default

[zachdaniel]

Resolves #1942

Changelog

Enhancements

• Exclude empty contracts by default from the unverified and not_decompiled filters. Add an empty filter to fetch contracts that have an empty bytecode.

  • 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 bdbcc483-c150-412a-b84e-996bced5453d

• 0 of 3 (0.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.1%) to 81.85%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
apps/block_scout_web/lib/block_scout_web/controllers/api/rpc/contract_controller.ex	0	1	0.0%
apps/explorer/lib/explorer/chain.ex	0	2	0.0%

Files with Coverage Reduction	New Missed Lines	%
apps/block_scout_web/lib/block_scout_web/channels/exchange_rate_channel.ex	1	50.0%

Totals
Change from base Build 24b8e670-bf87-4f35-bc1b-00ba852a442d:	0.1%
Covered Lines:	4654
Relevant Lines:	5686

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💛 - Coveralls