feat: don't make dest argument variadic

[yansal]

The API of the package is more clear if the dest argument of the Exec
function is not variadic. If users want to call the Exec function
without a dest argument, they can directly call driver.Exec instead.

[novln]

Destination (or output) is optional in this case, while I agree, most of the time we'll have something.

Using variadic for optional arguments is a known pattern in Go, while it's not the best, I think it's more simple/efficient to use (from an user perspective):

updateStmt := loukoum.Update("users").
    Set(loukoum.Pair("username", "novln")).
    Where(loukoum.Condition("username").Equal(1234))

makroud.Exec(ctx, driver, updateStmt)

Than,

makroud.Exec(ctx, driver, updateStmt, nil)

I'm not convinced by these changes. While I regret we can't have function overloading for this specific use case.

I don't have a better solution in my mind, but I think we could take advantage of this refactoring to merge RawExec and RawExecArgs, that basically does the same thing and has the same problems.

[yansal]

Using variadic for optional arguments is a known pattern in Go, while it's not the best, I think it's more simple/efficient to use (from an user perspective):

updateStmt := loukoum.Update("users").
Set(loukoum.Pair("username", "novln")).
Where(loukoum.Condition("username").Equal(1234))

makroud.Exec(ctx, driver, updateStmt)
Than,

makroud.Exec(ctx, driver, updateStmt, nil)

I would suggest to do the following instead:

query, args := loukoum.Update("users").
    Set(loukoum.Pair("username", "novln")).
    Where(loukoum.Condition("username").Equal(1234)).
    Query()
err := driver.Exec(ctx, query, args...)

I find it simpler because users just interacts with makroud.Driver, they don't need to interact with both makroud.Driver and makroud.Exec.