intel: Add executor tool

Add a tool that programs the hardware the minimum amount to be
able to execute compute shaders and then executes a script that
can perform data manipulation and dispatch execution of the shaders
(written in Xe assembly).

The goal is to have a tool to experiment directly with certain
assembly instructions and the shared units without having to
instrument the drivers.

To make more convenient to write assembly, a few macros (indicated by
the @-symbol) will be processed into the full instruction.

For example, the script

```
  local r = execute {
    data={ [42] = 0x100 },
    src=[[
      @mov     g1      42
      @read    g2      g1

      @id      g3

      add(8)   g4<1>UD  g2<8,8,1>UD  g3<8,8,1>UD  { align1 @1 1Q };

      @write   g3       g4
      @eot
    ]]
  }

  dump(r, 4)
```

produces

```
  [0x00000000] 0x00000100 0x00000101 0x00000102 0x00000103
```

There's a help message inside the code that describes the script
environment and the macros for assembly sources.

Acked-by: Ian Romanick <ian.d.romanick@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30062>

src/intel/executor/examples/help_example.lua

@@ -0,0 +1,18 @@
+-- Example from the help message.
+
+local r = execute {
+  data={ [42] = 0x100 },
+  src=[[
+    @mov     g1      42
+    @read    g2      g1
+
+    @id      g3
+
+    add(8)   g4<1>UD  g2<8,8,1>UD  g3<8,8,1>UD  { align1 @1 1Q };
+
+    @write   g3       g4
+    @eot
+  ]]
+}
+
+dump(r, 4)