Add support for literals in the SELECT clause. This allows
SELECT fn(column, 4) or SELECT fn(column, ?).
Note, "SELECT 7 FROM tab" becomes valid in the grammar, but is still
not accepted because of failed type inference - we cannot infer the
type of 7, and don't have a favored type for literals (like C favors
int). We might relax this later.
In the WHERE clause, and Cassandra in the SELECT clause, type hints
can also resolve type ambiguity: (bigint)7 or (text)?. But this is
deferred to a later patch.
A few changes to the grammar are needed on top of adding a `value`
alternative to `unaliasedSelector`:
- vectorSimilarityArg gained access to `value` via `unaliasedSelector`,
so it loses that alternate to avoid ambiguity. We may drop
`vectorSimilarityArg` later.
- COUNT(1) became ambiguous via the general function path (since
function arguments can now be literals), so we remove this case
from the COUNT special cases, remaining with count(*).
- SELECT JSON and SELECT DISTINCT became "ambiguous enough" for
ANTLR to complain, though as far as I can tell `value` does not
add real ambiguity. The solution is to commit early (via "=>") to
a parsing path.
Due to the loss of count(1) recognition in the parser, we have to
special-case it in prepare. We may relax it to count any expression
later, like modern Cassandra and SQL.
Testing is awkward because of the type inference problem in top-level.
We test via the set_intersection() function and via lua functions.
Example:
```
cqlsh> CREATE FUNCTION ks.sum(a int, b int) RETURNS NULL ON NULL INPUT RETURNS int LANGUAGE LUA AS 'return a + b';
cqlsh> SELECT ks.sum(1, 2) FROM system.local;
ks.sum(1, 2)
--------------
3
(1 rows)
cqlsh>
```
(There are no suitable system functions!)
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-296Closesscylladb/scylladb#28256
cc03f5c89d