[llvm] [Offload][OMPX] Add the runtime support for multi-dim grid and block (PR #118042)

[Jan Patrick Lehr via llvm-commits]

jplehr wrote:

I ran this through our buildbot config and the new tests do not seem to pass. The 0-th dimension appears to be the culprit. Can you double check that it works?
If you need any help / info, let me know.

```
# .---command stderr------------
# | llvm-project/offload/test/api/omp_env_vars.c:8:12: error: CHECK: expected string not found in input                                                                                                       
# |  // CHECK: Launching kernel [[KERNEL:.+_main_.+]] with [1,1,1] blocks and [1,1,1] threads
# |            ^
# | <stdin>:1:1: note: scanning from here
# | "PluginInterface" device 0 info: Launching kernel __omp_offloading_fd00_61c4b8b_main_l9 with [0,1,1] blocks and [0,1,1] threads in Generic mode                                                                                     
# | ^
# | <stdin>:1:55: note: possible intended match here
# | "PluginInterface" device 0 info: Launching kernel __omp_offloading_fd00_61c4b8b_main_l9 with [0,1,1] blocks and [0,1,1] threads in Generic mode                                                                                     
# |                                                       ^
# |
# | Input file: <stdin>
# | Check file: llvm-project/offload/test/api/omp_env_vars.c
# |
# | -dump-input=help explains the following input dump.
# |
# | Input was:
# | <<<<<<
# |            1: "PluginInterface" device 0 info: Launching kernel __omp_offloading_fd00_61c4b8b_main_l9 with [0,1,1] blocks and [0,1,1] threads in Generic mode                                                                       
# | check:8'0     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found                                                
# | check:8'1                                                           ?                                                                                          possible intended match                                              
# | >>>>>>
# `-----------------------------
# error: command failed with exit status: 1
```

https://github.com/llvm/llvm-project/pull/118042