Add SELECT ALL syntax, closes #18706

Why it matters

The addition of SELECT ALL provides an explicit syntax to indicate that all rows should be selected without any implicit uniqueness or filtering. This resolves ambiguity and improves compatibility with standard SQL syntax, making query intent clearer to users.

How to use it

Users can write queries using the new syntax as follows:

SELECT ALL <columns> FROM <table>;

This will explicitly select all rows from the specified table without applying any distinct or filtering logic.