[llvm] [mlir] [NFC][mlir][mesh,shard] Fixing misnomers in mesh dialect, renaming 'mesh' dialect to 'shard' (PR #150177)

[Mehdi Amini via llvm-commits]

https://github.com/joker-eph commented:

We should take this opportunity to improve the documentation as much as possible, in particular with reference to existing concepts. In particular since this is claiming that the original was a "misnomer", we should be able to anchor this in existing work out there.

https://github.com/llvm/llvm-project/pull/150177