dialects: merge snitch dialects

[superlopuh]

From experience trying to explain our lowerin in the paper and presentations, it seems that we have too many dialects to explain what's going on. I propose to move the riscv-specific operations to two dialects: snitch and riscv_snitch.

More concretely:

snitch_stream.* -> riscv_snitch
snitch.* -> riscv_snitch

[Edited]

[JosseVanDelm]

I tend to agree with this sentiment, but I'd check in with @jorendumoulin since he was planning to use a similar lowering approach for the snax streamers which is slightly different.
@jorendumoulin what are your thoughts on this?

[jorendumoulin]

hello yes!
For the first two, it definitely makes sense.
For the third, I am finally doing what I said I would be doing a month a ago and using the memref_stream for SNAX streamers.

It seems our lowering paths are like this:

                    ┌─────────────►  snitch_stream
                    │                             
                    │                             
linalg ────►  memref_stream                       
                                                  
                    │                             
                    │                             
                    └─────────────►  snax_stream  

I think the memref_stream abstraction definitely makes sense and is proving to be very useful for me. If merging the dialects means just moving over the operations, then fine (although memref_stream is quite snitch/risc-v-independent, so I'm not sure if this is logical). If it means actually changing the operations, this would be inconvenient for me.

[superlopuh]

That's interesting and a good point. Thank you very much for commenting on this as this is super useful feedback! In that case I'd probably want to just get rid of the snitch_stream dialect, and roll it into snitch, ending up with memref_stream, snitch, and riscv_snitch, where riscv_snitch has all the operations that can be printed as assembly, and snitch has everything else.