[d3d9] Tweak VCache query results

[WinterSnowfall]

I'm not entirely sure which games relied on this being exposed anyway, but here's a bit more insight into how this obscure query is supposed to work: https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/d3d9types/ns-d3d9types-_d3ddevinfo_vcache

Also this is what you get with native 45.23 Nvidia drivers, on Windows XP, with a GeForce 4:

Listing VCache query result:
  ~ vCache Pattern: CACH
  ~ vCache OptMethod: 1
  ~ vCache CacheSize: 16
  ~ vCache MagicNumber: 7

dxvk currently does:

Listing VCache query result:
  ~ vCache Pattern: HCAC
  ~ vCache OptMethod: 1
  ~ vCache CacheSize: 24
  ~ vCache MagicNumber: 20

Since I'm guessing CacheSize refers to the number of internal cached buffers the driver holds, it's probably safe to assume a d3d9-era card reported somewhat higher numbers (hence the doubling in this PR).

As for the 🪄 number, allegedly:

Typically, the best values are near CacheSize/2

... whatever that means. So copied over native behavior of CacheSize/2 - 1 here.

As far as I can tell, at least with d3d8, the results are entirely static, so this should be good enough. WineD3D actually just returns a bunch of gibberish.

I'll undraft this once I figure out what native drivers report these days.

[K0bin]

I fully agree with the comment we had in the code until now, so I don't really care.

// Don't know what the hell any of this means.
// Nor do I care. This just makes games work.

[WinterSnowfall]

The ATI/AMD results are in:

Native 8.65 ATI drivers, on Windows XP, with a HD 4650:

Listing VCache query result:
  ~ vCache Pattern: 0
  ~ vCache OptMethod: 0
  ~ vCache CacheSize: 0
  ~ vCache MagicNumber: 0

Native modern AMD, thanks to @Blisto91:

Listing VCache query result:
  ~ vCache Pattern: 0
  ~ vCache OptMethod: 0
  ~ vCache CacheSize: 0
  ~ vCache MagicNumber: 0

Glad to see some consistency. This would indicate the call succeeds, but the d3d8 specs are a bit wonky, in that the call should return S_FALSE if the query is not available (which is NOT a failure code), so d3d9 is probably right to report it as unsupported.

I'll wait until @Blisto91 can test native Nvidia, just to be sure we're not too far off the mark with my assumptions.

[WinterSnowfall]

Interestingly (thanks to @K0bin for the results), modern Nvidia also 0s things out, at least in d3d8:

Listing VCache query result:
  ~ Response: S_FALSE
  ~ Pattern: 0
  ~ OptMethod: 0
  ~ CacheSize: 0
  ~ MagicNumber: 0

Guess I'll check with my Nvidia FX 5500 and more recent drivers to see if the XP numbers change in any way.

[WinterSnowfall]

I've checked on the FX 5500 (the most modern Nvidia AGP card I have), with the latest drivers that released for XP before Vista came into the picture (namely 93.71), then checked a bunch of other intermediate drivers, and the query always returns:

Listing VCache query result:
  ~ vCache Pattern: CACH
  ~ vCache OptMethod: 1
  ~ vCache CacheSize: 16
  ~ vCache MagicNumber: 7

Seems to be a general default, so let's stick to that.

P.S.: A bunch of collected outputs can be found here: https://drive.google.com/drive/folders/1i0eTgX5IbcFdbZT1iPris9l1mqrpeSRf