Add support for function chaining and the dot syntax for function calls

[Mytherin]

This PR adds support for function chaining using the dot operator (see #6717).

For example:

Strings

CREATE TABLE varchars(str VARCHAR);
INSERT INTO varchars VALUES ('Hello World');
SELECT str.lower().split(' ')[1] AS res FROM varchars;
┌─────────┐
│   res   │
│ varchar │
├─────────┤
│ hello   │
└─────────┘

Lists

CREATE TABLE lists(ints INT[]);
INSERT INTO lists VALUES ([1, 5, 7, 9]), ([999, 1, 3, 7]), ([999, 4, 999]), ([999]);
SELECT ints.filter(x -> x < 999).apply(x -> x * 3).aggregate('sum') AS res FROM lists;
┌────────┐
│  res   │
│ int128 │
├────────┤
│     66 │
│     33 │
│     12 │
│   NULL │
└────────┘

The way it works is that whenever a function is called using the dot syntax, the left-side becomes the first parameter of the function. For example, str.lower() is equivalent to lower(str). This allows more convenient chaining of multiple functions without having to deeply nest function calls.

[douenergy]

Dr. @Mytherin you are a ducking magician 🦆🎩