Adding support of MAP_TOP_N_KEYS to Presto

[jainavi17]

Add an UDF for getting top N keys of a map, which returns an array of the top N keys of map. Optionally a lambda comparator can also be passed to perform a custom comparison of the values. Returns all the value if the value N is greater than or equal to size of the map. N must be >= 0. For N = 0, the function returns empty array.

map_top_n_keys(map(K, V), N) -> array(K)

• For N > 0, returns the top N keys of a map. If N happens to larger than size of the map, it returns all the keys of the map in descending order
• For N = 0, return empty array
• For N < 0, function throws an error.

map_top_n_keys(map(K, V), N, function(K, K, int)) -> array(K)
Return the top N keys of the map sorted using the lambda comparator.

Test plan - (Please fill in how you tested your changes)
Added unit tests.
Build successfully using the following terminal command

• ./mvnw clean install -Dtest=TestMapTopNKeysFunction -fn -pl presto-main
• ./mvnw clean install -Dtest=TestMapTopNKeysComparatorFunction -fn -pl presto-main

Fill in the release notes towards the bottom of the PR description.
See Release Notes Guidelines for details.

== RELEASE NOTES ==

General Changes
* Add support for MAP_TOP_N_KEYS
* Returns an array of the top N keys of map. Optionally a lambda comparator can also be passed to perform a custom comparison of the keys. Returns all the keys if the value N is greater than or equal to size of the map. For N < 0, the function returns keys in the reverse order. For N = 0, the function returns empty array.

.. function:: map_top_n_keys(map(K, V), N) -> array(K)
   Returns the top N keys of ``map``. If N must be >= 0. For N = 0, it returns empty ``array``.

.. function:: map_top_n_keys(map(K, V), N, function(K, K, int)) -> array(K)
   Returns the top N keys of ``map`` sorted using lambda comparator. N must be >= 0. For N = 0, it returns empty ``array``.

`SELECT MAP_TOP_N_KEYS(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 2)); -- 6, 5`
`SELECT MAP_TOP_N_KEYS(MAP(ARRAY['a', 'b', 'c', 'd'], ARRAY[1, 2, 3, NULL, NULL]), -3)); -- 'a', 'b', 'c'`
`SELECT MAP_TOP_N_KEYS(MAP(ARRAY[4, 5, 6], ARRAY[1, 2, 3]), 4, (x, y) -> IF(x < y, 1, IF(x = y, 0, -1))); -- 4, 5, 6`

[linux-foundation-easycla]

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• ✅ login: jainavi17 / name: Avinash Jain (ae9c23c5f094d38214b7b5dbecceef40151b3040)

[jainavi17]

Can we merge this?