Wrong ast.Unnest in FROM INFORMATION_SCHEMA.TABLES

[apstndb]

Currently, FROM INFORMATION_SCHEMA.* are parsed as ast.Unnest.

$ go run ./tools/parse --mode query 'SELECT * FROM INFORMATION_SCHEMA.TABLE'
--- AST
&ast.QueryStatement{
  Hint:  (*ast.Hint)(nil),
  With:  (*ast.With)(nil),
  Query: &ast.Select{
    Select:   0,
    Distinct: false,
    AsStruct: false,
    Results:  []ast.SelectItem{
      &ast.Star{
        Star: 7,
      },
    },
    From: &ast.From{
      From:   9,
      Source: &ast.Unnest{
        Unnest:   -1,
        Rparen:   -1,
        Implicit: true,
        Expr:     &ast.Path{
          Idents: []*ast.Ident{
            &ast.Ident{
              NamePos: 14,
              NameEnd: 32,
              Name:    "INFORMATION_SCHEMA",
            },
            &ast.Ident{
              NamePos: 33,
              NameEnd: 38,
              Name:    "TABLE",
            },
          },
        },
        Hint:       (*ast.Hint)(nil),
        As:         (*ast.AsAlias)(nil),
        WithOffset: (*ast.WithOffset)(nil),
        Sample:     (*ast.TableSample)(nil),
      },
    },
    Where:   (*ast.Where)(nil),
    GroupBy: (*ast.GroupBy)(nil),
    Having:  (*ast.Having)(nil),
    OrderBy: (*ast.OrderBy)(nil),
    Limit:   (*ast.Limit)(nil),
  },
}

--- SQL
SELECT * FROM INFORMATION_SCHEMA.TABLE

I think it is fixed after #100.

[apstndb]

Note: handy-spanner relies on this behavior
https://github.com/gcpug/handy-spanner/blob/912f0bb8d89eb5fafcade86f3fec3b1aa93266e9/server/query.go#L612-L629