Fix read contract bytes array type output

[vbaranov]

Motivation

Error at "Read contract" page if a contract contains bytes array type.

blockscout     | Request: GET /smart_contracts?hash=0xe7d982c6554e490ee707144d2f38a1c1ca3ccaae&type=regular&action=read
blockscout     | ** (exit) an exception was raised:
blockscout     |     ** (ArgumentError) argument error
blockscout     |         :erlang.byte_size([<<238, 151, 199, 221, 46, 115, 76, 242, 52, 194, 186, 13, 131, 167, 70, 51, 225, 172, 127, 200, 169, 253, 119, 159, 132, 151, 160, 16, 156, 113, 185, 147>>, <<165, 241, 91, 31, 169, 32, 187, 219, 194, 143, 93, 120, 94, 82, 36, 227, 166, 110, 181, 247, 212, 9, 45, 201, 186, 130, 213, 229, 174, 58, 188, 135>>, <<94, 248, 58, 217, 85, 144, 51, 230, 233, 65, 219, 125, 124, 73, 90, 205, 206, 97, 99, 71, 210, 142, 144, 199, 206, 71, 203, 252, 252, 173, 59, 197>>, <<58, 71, 171, 91, 211, 165, 148, 195, 168, 153, 95, 143, 165, 141, 8, 118, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0>>, <<58, 71, 171, 91, 211, 165, 148, 195, 168, 153, 95, 143, 165, 141, 8, 118, 201, 104, 25, 202, 69, 22, 189, 118, 16, 12, 146, 70, 47, 47, 157, 192>>])
blockscout     |         (explorer 0.0.1) lib/explorer/smart_contract/reader.ex:343: Explorer.SmartContract.Reader.bytes_to_string/1
blockscout     |         (explorer 0.0.1) lib/explorer/smart_contract/reader.ex:325: Explorer.SmartContract.Reader.new_value/3
blockscout     |         (explorer 0.0.1) lib/explorer/smart_contract/reader.ex:316: anonymous fn/3 in Explorer.SmartContract.Reader.link_outputs_and_values/3
blockscout     |         (elixir 1.10.2) lib/enum.ex:2111: Enum."-reduce/3-lists^foldl/2-0-"/3
blockscout     |         (explorer 0.0.1) lib/explorer/smart_contract/reader.ex:315: Explorer.SmartContract.Reader.link_outputs_and_values/3
blockscout     |         (explorer 0.0.1) lib/explorer/smart_contract/reader.ex:233: Explorer.SmartContract.Reader.fetch_current_value_from_blockchain/3
blockscout     |         (elixir 1.10.2) lib/enum.ex:1396: Enum."-map/2-lists^map/1-0-"/2

Changelog

Properly format output value in case of bytes array type

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