panfrost: Map PIPE_{DXT, RGTC, BPTC} to MALI_BCn

panfrost: Map PIPE_{DXT, RGTC, BPTC} to MALI_BCn

Mali (and Vulkan) uses D3D naming conventions for these formats where
Gallium/Mesa uses OpenGL names, but the formats are equivalent. sRGB is
communicated out-of-band on Mali; otherwise, it appears to be a 1:1
mapping.

On supported devices, this exposes GL_EXT_texture_compression_rgtc and
GL_ARB_texture_compression_bptc, so update features.txt

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5856>