Handle array states and values in assertTableColumnStateSet

[cheesegrits]

Description

Allows assertTableColumnStateSet() (and NotSet) to be used for testing columns with array states, such as when rendering a dotted relation with multiple values.

No backward compat issues, doesn't affect any existing usage of these methods, only has any effect if the column state or the expected value are arrays.

Prior to this PR, attempting to test an array value against an array state would error out, because the code assumed $value was stringable when composing the failure message (so "array to string conversion" error). By serializing the state and/or value, this avoids that error, and also avoids potential array comparison issues (by comparing the serialized versions).

Visual changes

No visual changes

Functional changes

• Code style has been fixed by running the composer cs command.
• Changes have been tested to not break existing functionality.
• Documentation is up-to-date.