Previously, whitespace in between the keys and values in the JSON was
not trimmed correctly in BasicJsonParser which lead to it incorrectly
parsing JSON with whitespace between the opening of a list ([) and the
opening of a map ({).
This commit updates the parser to trim unwanted whitespace and adds a
test to AbstractJsonParserTests to verify the whitespace handling
behaviour across all JsonParser implementations.
Closes gh-18911
a11661d284