`JimpInstance` type can't be used consistently when working with Jimp instances

# Expected Behavior

Before v1, it was possible to pass around `Jimp` as a type and throw in the results of `Jimp.read`/`Jimp.create`/`new Jimp`. Example without TS errors:

```ts
import Jimp from "jimp"

const img1 = await Jimp.read("")
const img2 = await Jimp.create("")
const img3 = new Jimp("")

function test(j: Jimp) {}

test(img1) // works
test(img2) // works
test(img3) // works
```

See https://codesandbox.io/p/sandbox/g56q6v?file=%2Findex.mts

# Current Behavior

#1330 already added an improvement via the `JimpInstance` type, but it seems like it doesn't work the same way (interchangeably).

```ts
import { Jimp, JimpInstance } from "jimp";

const inst = new Jimp({ width: 100, height: 100 });
const img = await Jimp.read("…");

function testInstance(j: JimpInstance) {}
function testRead(j: Awaited>) {}

testInstance(img); // error
testRead(img);

testInstance(inst);
testRead(inst); // error
```

See https://codesandbox.io/p/sandbox/jimp-test-249ch8-pk8qdr?file=%2Findex.mts

Workaround for now is to use `Awaited>`

# Failure Information (for bugs)

## Steps to Reproduce

- 0.22.12 behaviour: https://codesandbox.io/p/sandbox/g56q6v?file=%2Findex.mts
- 1.6.0 behaviour: https://codesandbox.io/p/sandbox/jimp-test-249ch8-pk8qdr?file=%2Findex.mts

---

Ref. https://github.com/jimp-dev/jimp/issues/1328#issuecomment-2337770442