[fingerprint] revamp config-plugins sourcer (#24520)

# Why

originally, for local config-plugins we will include the entire app directory from generating fingerprints. in this state, fingerprint i

[fingerprint] revamp config-plugins sourcer (#24520)

# Why

originally, for local config-plugins we will include the entire app directory from generating fingerprints. in this state, fingerprint is kind of useless, e.g. just updating README.md will have new fingerprint. this pr tries to follow local config-plugins dependencies and only includes necessary files from hashing.

# How

based on Evan's great suggestion, to create a process to call `getConfig()` and inspect the loaded modules by `module._cache`. this pr introduces a **ExpoConfigLoader.js** to load that. also passing ignoredPaths to the loader so that we don't have to pass the known/useless loadedModules back to caller process.

show more ...