Adding support of MAP_REMOVE_NULL_VALUES for Presto

[jainavi17]

Adding support of MAP_REMOVE_NULL_VALUES for Presto.

map_remove_null_values(map(K, V)) -> map(K, V)

Test plan
Added unit tests.
Build successfully using the following terminal command

• mvn -Dtest=TestMapRemoveNullValuesFunction test

== RELEASE NOTES ==

General Changes
* Add :func:`map_remove_null_values` to remove all the entries where the value is null from the given map

[v-jizhang]

@bot kick off tests

[kaikalur]

Maybe call it MAP_REMOVE_NULL_VALUES? Not sure.

Also add documentation

[jainavi17]

Maybe call it MAP_REMOVE_NULL_VALUES? Not sure.

Also add documentation

I think MAP_REMOVE_NULLS also works given keys can't be null. Also users can always refer to documentation if they have doubts.

Let me add documentation.

[jainavi17]

Documentation added.

[kaikalur]

Maybe call it MAP_REMOVE_NULL_VALUES? Not sure.
Also add documentation

I think MAP_REMOVE_NULLS also works given keys can't be null. Also users can always refer to documentation if they have doubts.

Let me add documentation.

No we should be explicit as far as possible users should understand without any other knowledge. So I say call it MAP_REMOVE_NULL_VALUES

[jainavi17]

hould understand witho

No we should be explicit as far as possible users should understand without any other knowledge. So I say call it MAP_REMOVE_NULL_VALUES

OK

[jainavi17]

Can we merge this one?