Update SK_IMAGE_VERSION to test RAW

Update SK_IMAGE_VERSION to test RAW

Bump SK_IMAGE_VERSION to test the images in v2 in GoogleStorage, which
includes the images from v1 plus test images for SkRawCodec.

Only define skia_decodes_raw on platforms that support it, rather than
defining it always and checking additional conditions to determine
whether to support raw. Further, define it and SK_CODEC_DECODES_RAW
for all targets, so we can use the compile flag in other targets.

In DM, exclude the raw extensions if SK_CODEC_DECODES_RAW is not defined.

Blacklist raw extensions on NexusPlayer, which was running out of memory
when running them.

BUG=skia:4829

GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1612113002

Review URL: https://codereview.chromium.org/1612113002