better statement splitter

[ruslandoga]

Preparing for https://hexdocs.pm/ecto_sql/Ecto.Adapters.SQL.html#query_many/4

Context: plausible/analytics#4701 (comment)

TODOs:

• https://clickhouse.com/docs/en/sql-reference/syntax#heredoc
• more tests
• copy some of stateless ClickHouse parser tests?
• property tests? with "random" quote / comment / semicolon injection

check all(statements <- gen_statements()) do
  assert extract_statements(Enum.join(statements, ";")) == statements
  # and maybe execute them in ClickHouse
end

defp gen_statements do
  for str <- string(:printable) do
    "select '#{str}'"
  end
  
  # etc. and union them all
end