Fix serializeValue to properly handle slices

[reginaldl]

This change fixes serialization of slices when passed as argument to Evaluate(). I found two issues with how slices are serialized:

• The original argument was directly modified (passed as a reference) to become a map. We now create a separate map.
• Once serialized, we returned a slice of map which I believe is not expected. We now returned {"a": [..]}, which is what the python library does here.

I also added a few tests.

I discovered that passing floats and time will not work. We do not correctly serialize valid floats but when I tried fixing it I got the following error: playwright: arg.value.v: expected one of (null|undefined|NaN|Infinity|-Infinity|-0)

Unfortunately, I wasn't able to fix this.

[canstand]

Thank you @reginaldl. There are multiple issues with serializeValue. I'll address it overall with another PR.

[canstand]

@reginaldl #412 merged and add you as co-authored.

[canstand]

close due to #412