Drop base_symbols

[hadley]

• NULL doesn't do anything
• * errors with "cannot translate a primitive function to SQL"
• pi mismatches to columns in select(), and in mutate() it's already inlined

Fixes #1531

Before:

library(dbplyr)
library(dplyr, warn.conflicts = FALSE)

lf <- lazy_frame(x = 1, y = 2, pi = 2)
# Incorrect uses function
lf |> select(pi) |> show_query()
#> <SQL>
#> SELECT PI() AS `pi`
#> FROM `df`
# Already inlines pi
lf |> select(x) |> mutate(y = pi) |> show_query()
#> <SQL>
#> SELECT `x`, 3.14159265358979 AS `y`
#> FROM `df`
# Errors
lf |> mutate(y = count(`*`)) |> show_query()
#> Error:
#> ! Cannot translate a primitive function to SQL.
#> ℹ Do you want to force evaluation in R with (e.g.) `!!x` or `local(x)`?
# Already works
lf |> mutate(y = f(1, NULL)) |> show_query()
#> <SQL>
#> SELECT `x`, f(1.0, NULL) AS `y`, PI() AS `pi`
#> FROM `df`

^{Created on 2025-12-08 with reprex v2.1.1}

After

library(dbplyr)
library(dplyr, warn.conflicts = FALSE)

lf <- lazy_frame(x = 1, y = 2, pi = 2)
# Incorrect uses function
lf |> select(pi) |> show_query()
#> <SQL>
#> SELECT `pi`
#> FROM `df`
# Already inlines pi
lf |> select(x) |> mutate(y = pi) |> show_query()
#> <SQL>
#> SELECT `x`, 3.14159265358979 AS `y`
#> FROM `df`
# Errors
lf |> mutate(y = count(`*`)) |> show_query()
#> Error:
#> ! Cannot translate a primitive function to SQL.
#> ℹ Do you want to force evaluation in R with (e.g.) `!!x` or `local(x)`?
# Already works
lf |> mutate(y = f(1, NULL)) |> show_query()
#> <SQL>
#> SELECT `x`, f(1.0, NULL) AS `y`, `pi`
#> FROM `df`

^{Created on 2025-12-08 with reprex v2.1.1}