Missing P/Invokes for publicly documented Dism methods like `DismOpenSession`, etc.

Nobody has claimed this yet.

## Actual behavior

I'm trying to do some stuff with Dism, and the first thing I need is [`DismOpenSession()`](https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/dism/dismopensession-function?view=windows-11) but it's not available. I'm not sure if this is a CsWin32 thing or a win32metadata thing.

## Expected behavior

That this P/Invoke exist, along with all other publicly documented methods.

## Repro steps

1. `NativeMethods.txt` content:
```
DismOpenSession
```

2. `NativeMethods.json` content (if present): N/A

3. Any of your own code that should be shared? N/A

### Context

- CsWin32 version: 0.3.275
- Win32Metadata version (if explicitly set by project): N/A
- Target Framework: net472
- `LangVersion` (if explicitly set by project): latest

Start with the DismOpenSession entry point and the NativeMethods.txt request shown in the issue, then compare the win32metadata representation with how CsWin32 resolves it. The NativeMethods.json example is marked N/A, so determine which metadata source is missing the publicly documented Dism methods. Done means DismOpenSession and the other documented methods generate P/Invokes from NativeMethods.txt.

Written by the indexing model from the issue text.