feat: support proxying functions with explicit properties

[wingsbob]

Ran into an issue where functions which have had properties assigned to them were stripped off when upgrading from nestjs-cls@3 to nestjs-cls@4 and above

I believe this should illustrate where this was an issue:

import { ClsModule } from 'nestjs-cls';

export const PROVIDER_SYMBOL = Symbol();

export class ContrivedExample {
  public property: (() => void) & { foo: string; bar: { baz: string } };
  constructor() {
    const someFunction = () => {};

    this.property = Object.assign(someFunction, {
      foo: 'foo',
      bar: { baz: 'baz' },
    });
  }
}
export const ContrivedExampleModule = ClsModule.forFeatureAsync({
  provide: PROVIDER_SYMBOL,
  imports: [],
  inject: [],
  useFactory: () => new ContrivedExample(),
});

This is just hooking the example up to a controller

import { Module } from '@nestjs/common';
import { HealthController } from './health.controller';
import { ContrivedExampleModule } from '../example.module';

@Module({
  imports: [ContrivedExampleModule],
  controllers: [HealthController],
})
export class HealthModule {}

When we try to access things within the controller, we see that the properties have mysteriously vanished

import { Controller, Get, Inject } from '@nestjs/common';
import { PROVIDER_SYMBOL, type ContrivedExample } from '../example.module';

@Controller('health')
export class HealthController {
  constructor(
    @Inject(PROVIDER_SYMBOL) private readonly example: ContrivedExample
  ) {}
  @Get()
  getHealth(): { status: 'ok' } {
    this.example.property(); // Works just fine
    console.log(this.example.property.bar.baz); // Errors as `bar` is undefined due to `property` being bound
    return { status: 'ok' };
  }
}

[Papooch]

Hi, sorry, I only noticed this PR now. Thank you for the fix! Can I also ask you to include a test case for this behavior?