Eliminate `nvgpu::` prefix in several places.

This patch introduces the `LLVMAddrSpaceAttrInterface` for defining
compatible LLVM address space attributes

To test this interface, this patch also adds:
- Adds NVVMMemorySpaceAttr implementing both LLVMAddrSpaceAttrInterface
and MemorySpaceAttrInterface
- Converts NVVM memory space constants from enum to MLIR enums
- Updates all NVVM memory space references to use new attribute system
- Adds support for NVVM memory spaces in ptr dialect translation

Example:
```mlir
llvm.func @nvvm_ptr_address_space(
    !ptr.ptr<#nvvm.memory_space<global>>,
    !ptr.ptr<#nvvm.memory_space<shared>>,
    !ptr.ptr<#nvvm.memory_space<constant>>,
    !ptr.ptr<#nvvm.memory_space<local>>,
    !ptr.ptr<#nvvm.memory_space<tensor>>,
    !ptr.ptr<#nvvm.memory_space<shared_cluster>>
  ) -> !ptr.ptr<#nvvm.memory_space<generic>>
```
Translating the above code to LLVM produces:
```llvm
declare ptr @nvvm_ptr_address_space(ptr addrspace(1), ptr addrspace(3), ptr addrspace(4), ptr addrspace(5), ptr addrspace(6), ptr addrspace(7))
```


To convert the memory space enum to the new enum class use:
```bash
grep -r . -e "NVVMMemorySpace::kGenericMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kGenericMemorySpace/NVVMMemorySpace::Generic/g"
grep -r . -e "NVVMMemorySpace::kGlobalMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kGlobalMemorySpace/NVVMMemorySpace::Global/g"
grep -r . -e "NVVMMemorySpace::kSharedMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kSharedMemorySpace/NVVMMemorySpace::Shared/g"
grep -r . -e "NVVMMemorySpace::kConstantMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kConstantMemorySpace/NVVMMemorySpace::Constant/g"
grep -r . -e "NVVMMemorySpace::kLocalMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kLocalMemorySpace/NVVMMemorySpace::Local/g"
grep -r . -e "NVVMMemorySpace::kTensorMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kTensorMemorySpace/NVVMMemorySpace::Tensor/g"
grep -r . -e "NVVMMemorySpace::kSharedClusterMemorySpace" -l | xargs sed -i -e "s/NVVMMemorySpace::kSharedClusterMemorySpace/NVVMMemorySpace::SharedCluster/g"
```

NOTE: A future patch will add support for ROCDL, it wasn't added here to
keep the patch small.

Change local variants to use new central one.

This reverts commit 228c45f13dc92546661b6825b7b32c3808b0d2eb (PR
#148937) . Now that #148027 is landed, I think it is safe to "reland"
the original PR: #148028

See https://github.com/llvm/llvm-project/pull/147168 for more info.

This reverts PR/commit https://github.com/llvm/llvm-project/commit/99875733fce0c6c72c50244ceaffe0cc5e1fa277

This PR/commit should only be landed after
https://github.com/llvm/llvm-project/pull/148027, at which point we
don't need to assume that vector.broadcast has been lowered to another
form. 

Part of deprecation of vector.splat

RFC:
https://discourse.llvm.org/t/rfc-mlir-vector-deprecate-then-remove-vector-splat/87143/4
More complete deprecation:
https://github.com/llvm/llvm-project/pull/147818

This patch fixes warnings of the form:

  mlir/lib/Conversion/VectorToGPU/VectorToGPU.cpp:320:19: error:
  unused variable 'result' [-Werror,-Wunused-variable]

The current implementation of getBackwardSlice will crash if an
operation in the dependency chain is defined by an operation with
multiple regions or blocks. Crashing is bad (and forbids many analyses
from using getBackwardSlice, as well as causing existing users of
getBackwardSlice to fail for IR with this property).

This PR instead causes the analysis to return a failure, rather than
crash in the cases it cannot compute the full slice

---------

Co-authored-by: Oleksandr "Alex" Zinenko <git@ozinenko.com>

[mlir][vector] Standardize base Naming Across Vector Ops (NFC)

This change standardizes the naming convention for the argument
representing the value to read from or write to in Vector ops that
interface with Tensors or MemRefs. Specifically, it ensures that all
such ops use the name `base` (i.e., the base address or location to
which offsets are applied).

Updated operations:

* `vector.transfer_read`,
* `vector.transfer_write`.

For reference, these ops already use `base`:

* `vector.load`, `vector.store`, `vector.scatter`, `vector.gather`,
  `vector.expandload`, `vector.compressstore`, `vector.maskedstore`,
  `vector.maskedload`.

This is a non-functional change (NFC) and does not alter the semantics of these
operations. However, it does require users of the XFer ops to switch from
`op.getSource()` to `op.getBase()`.

To ease the transition, this PR temporarily adds a `getSource()` interface
method for compatibility. This is intended for downstream use only and should
not be relied on upstream. The method will be removed prior to the LLVM 21
release.

Implements #131602