arrow

GH-38589: [C++][Gandiva] Support registering external C functions (#38632)

### Rationale for this change
This PR tries to enhance Gandiva by supporting registering external C functions to its function registry, so that developers can author third party functions with complex dependency and expose them as C functions to be used in Gandiva expression. See more details in GH-38589.

### What changes are included in this PR?
This PR primarily adds a new API to the `FunctionRegistry` so that developers can use it to register external C functions:
```C++
arrow::Status Register(
      NativeFunction func, void* c_function_ptr,
      std::optional<FunctionHolderMaker> function_holder_maker = std::nullopt);
```

### Are these changes tested?
* The changes are tested via unit tests in this PR, and the unit tests include several C functions written using C++ and we confirm this kind of functions can be used by Gandiva after registration using the above mentioned new API.
* Additionally, locally I wrote some Rust based functions, and integrate the Rust based functions into a C++ program by using the new registration API and verified this approach did work, but this piece of work is not included in the PR.

### Are there any user-facing changes?
There are several new APIs added to `FunctionRegistry` class:
```C++
/// \brief register a C function into the function registry
  /// @ param func the registered function's metadata
  /// @ param c_function_ptr the function pointer to the
  /// registered function's implementation
  /// @ param function_holder_maker this will be used as the function holder if the
  /// function requires a function holder
  arrow::Status Register(
      NativeFunction func, void* c_function_ptr,
      std::optional<FunctionHolderMaker> function_holder_maker = std::nullopt);

  /// \brief get a list of C functions saved in the registry
  const std::vector<std::pair<NativeFunction, void*>>& GetCFunctions() const;

  const FunctionHolderMakerRegistry& GetFunctionHolderMakerRegistry() const;
```

* Closes: #38589

### Notes
* This PR is related with https://github.com/apache/arrow/pull/38116, which adds the initial support for registering LLVM IR based external functions into Gandiva.

Authored-by: Yue Ni <niyue.com@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>