Introduce APIs In Bundled Program to Not Take **Method** When Loading Input

[zhenyan-zhang-meta]

Context

This issue is the first step of #9638. In the discussion, we want to unblock having extension/module as the single source of implementation, which means that pybindings/pybindings should use extension/module rather than its own.

Specifically, the thing we need to unblock is that pybindings/pybindings needs to load bundled program, and the current BundledProgram APIs take method module as input (e.g. executorch::bundled_program::load_bundled_input), where Extension.module does not expose method class. Therefore we need to introduce new APIs to do the same job without exposing method, wrap as a form of BundledModule.

As a first step, we want to introduce a new API in BundledProgram to get bundled program input out of the program without taking method.

Proposal

The proposed change includes a utility function to the bundled program.

// in bundled_program.bundled_program.h

/**
  * Load testset_idx-th bundled input of method_name into given data_ptr 
  */
ET_NODISCARD ::executorch::runtime::Error get_bundled_input(
    SerializedBundledProgram* bundled_program_ptr,
    char* method_name,
    size_t testset_idx,
    void* data_ptr,
    size_t data_length);

With this API, we are able to unblocked implementation the bundled module wrapper for pybindings.