test(lib): ensure list mapper does not fail when passed IResolvables

[DanielMSchmidt]

Closes #1788
Closes #910
Closes #835

[ansgarm]

.

[jsteinich]

I believe #835 has been fixed, but I'm not yet convinced that #910 still doesn't cause issues.

I haven't quite thought of a case where this would actually happen, but if deepMerge ends up mixing tokens and non-tokens within the same property the results could be wrong.
Another spot worth testing is Lazy. We don't really use it, but it does exist.

[DanielMSchmidt]

if deepMerge ends up mixing tokens and non-tokens within the same property the results could be wrong.

on the same property as in different types of tokens in a list or as function invocations?

[jsteinich]

if deepMerge ends up mixing tokens and non-tokens within the same property the results could be wrong.

on the same property as in different types of tokens in a list or as function invocations?

A couple possible cases:

• Trying to merge a token and non-token. One direct just overwrites, the other might append to the token object.
• Adding token and non-token to list. Resolution will fail later.

@ansgarm there was a slack thread recently about JSON.stringify; would that line up with this.

[ansgarm]

Yeah, I just filed an issue for the JSON.stringify problem: #1796
There was also this one, but that is a separate issue: #1795

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