Symbolic macros do not check allowed attribute values

### Description of the bug:

Both rules and symbolic macros support `attr.string()` with a `values` parameter. However, only rules raise an error if an unlisted value is specified.

### Which category does this issue belong to?

Loading API

### What's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

`defs.bzl`:
```
def _my_macro_impl(name, bar, visibility):
native.filegroup(name = name)

my_macro = macro(
implementation = _my_macro_impl,
attrs = {
"bar": attr.string(
values = ["a", "b", "c"],
),
},
)

def _my_rule_impl(ctx):
pass

my_rule = rule(
implementation = _my_rule_impl,
attrs = {
"bar": attr.string(
values = ["a", "b", "c"],
),
},
)
```

`BUILD.bazel`:
```
load("defs.bzl", "my_macro", "my_rule")

my_macro(
name = "a_macro_target",
bar = "d",
)

my_rule(
name = "a_rule_target",
bar = "d",
)
```

The following error is reported for `a_rule_target` but not for `a_macro_target`:
`invalid value in 'bar' attribute: has to be one of 'a', 'b', or 'c' instead of 'd'`

### Which operating system are you running Bazel on?

Linux

### What is the output of `bazel info release`?

release 8.2.1

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse HEAD` ?

```text

```

### If this is a regression, please try to identify the Bazel commit where the bug was introduced with bazelisk --bisect.

_No response_

### Have you found anything relevant by searching the web?

_No response_

### Any other information, logs, or outputs that you want to share?

_No response_