filter does not work in UnitTestTree

### Command

generate

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

_No response_

### Description

`filter()` does not work when applied to a `UnitTestTree`

I believe this is because `UnitTestTree` is not a `HostTree`

### Minimal Reproduction

https://github.com/cheng93/angular-schematics-filter

run the test in the `hello-world` schematics

### Exception or Error

```text
Error: Tree type is not supported.
```

### Your Environment

```text
_ _ ____ _ ___
/ \ _ __ __ _ _ _| | __ _ _ __ / ___| | |_ _|
/ △ \ | '_ \ / _` | | | | |/ _` | '__| | | | | | |
/ ___ \| | | | (_| | |_| | | (_| | | | |___| |___ | |
/_/ \_\_| |_|\__, |\__,_|_|\__,_|_| \____|_____|___|
|___/

Angular CLI: 16.1.8
Node: 20.0.0 (Unsupported)
Package Manager: npm 9.6.4
OS: win32 x64

Angular: 16.2.8
... animations, common, compiler, compiler-cli, core, forms
... platform-browser, platform-browser-dynamic, router

Package Version
------------------------------------------------------
@angular-devkit/architect 0.1601.8
@angular-devkit/core 16.1.8
@angular-devkit/schematics 16.1.8
@angular/cli 16.1.8
@schematics/angular 16.1.8
rxjs 7.8.1
typescript 5.1.6
zone.js 0.13.3
```

### Anything else relevant?

_No response_

Inizia con la riproduzione collegata di angular-schematics-filter ed esegui il relativo test delle schematics hello-world. Traccia il modo in cui filter() gestisce UnitTestTree e confronta questo percorso con l’errore unsupported-tree segnalato. Il lavoro è completato quando l’operazione di filtro funziona su UnitTestTree e il test di riproduzione ha esito positivo.

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