fix: previously unsurported array-style query variants

[tsebas]

There seems to be a lack of standardization when it comes to encoding arrays in the query parameters, in general.

1. The now deprecated request module for example seems to use the indexed array approach, foo[0]=bar1&foo[2]=bar2.
2. Axios seems to prefer the unindexed array approach, i.e. foo[]=bar1&foo[]=bar2
3. there is also the implicit array approach where the parameter becomes an array if it appears multiple times, i.e. foo=bar1&foo=bar2

Nock is able to handle 1 and 3 with the current code, but not 2, which is the default serialization from Axios. One could in principle just resort to a different serialization, and in fact axios support the option of serializing the parameters if any of the above approaches. However, it makes sense for Nock to support cleanly all 3 since it is being used to test APIs and for that reason it shouldn't be enforcing 1 approach over another.

[tsebas]

It adds 1 test for case 2, and unlike the other tests it focuses only on array parsing, and it doesn't mix other kinds of parameters. While I disagree in general with the exact structure of those tests, I can make mine look more like them, by adding handling of other parameters as well.

Ps.: I was going to submit a Github issue, but since the code turned out easy to understand, modify and test, I decided to just proceed with that instead. Please let me know if you'd want me to follow another process, if this is inadequate.