[#628] Remove raw bytestring literals from tests

Description

Problem: There are some usages of raw bytestring literals in Test.Morley.Expression. They are less readable and convenient than hex-encoded strings, which we usually use.

Solution: Raw bytestring literals were replaced by hex encoded strings. Also deleted some duplicates of unsafeFromHex from Cleveland.Util.

Related issue(s)

None

Resolves #628 (closed)

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