[Enhancment] Calling `expectSelfie()` from another package

Hello, the library is pretty useful, but I'm stumbling into a problem that I'm not sure how to fix.

Using Kotest, I want to create a reusable `Spec` to snapshot tests my custom exceptions and their localization.
It ends up looking kind of like this:

```kt
package mypackage.errors

abstract class ErrorSpec(
private val clazz: KClass,
private val create: () -> T
) :
FunSpec({
context("Localisation") {
forAll(Exhaustive.collection(SUPPORTED_LOCALES)) {

expectSelfie(json.encodeToString(clazz.serializer(), create())).toMatchDisk()

}
}
})

class ErrorTest : ErrorSpec(
clazz = Error::class,
create = { Error() }
)
```

This work perfectly, until I put `ErrorSpec` in another package.
The main reason I want to do this is to use a `testFixtures`.

This then ends up failing at runtime with:

```
org.opentest4j.AssertionFailedError:
Couldn't find source file for CallLocation(
clazz=mypackage.ErrorSpec$1$1,
method=invokeSuspend,
fileName=Specs.kt,
line=36
),

looked in TypedPath(absolutePath=[...]/mypackage/src/test/kotlin/)
and [[...]/mypackage/src/test/resources],

maybe there are other source roots?
```

What I don't understand is that, if I use `toMatchDisk_TODO()` instead of `toMatchDisk()`, the snapshot files end up being written, but the tests fails on `writeLine`.

Manually changing the value of `isTodo` to `true` in `SelfieImplementations/DiskSelfie.toMatchDisk():38`, the tests pass successfully, with the snapshot file being written at the correct place (albeit being overwritten every run, which kind of defeat the point).

Is there a way to do what I want using the public API?
If not, would it be possible to implement?

Inizia riproducendo l’esempio ErrorSpec tra package e ispeziona SelfieImplementations/DiskSelfie.toMatchDisk(), in particolare il comportamento intorno alla riga 38 e la ricerca del sorgente di CallLocation. Confrontalo con toMatchDisk_TODO(). È completato quando l’API pubblica può convalidare e scrivere snapshot da un altro package senza basarsi sul comportamento di TODO o sovrascriverli a ogni esecuzione.

Scritto dal modello di indicizzazione a partire dal testo della issue.