feat: add call_function_accel C function to accel.c

Add the call_function_accel function directly to accel.c, implementing
a combined load/call/dump operation for UDF function calls. This function
handles rowdat_1 deserialization, Python UDF invocation, and result
serialization in a single optimized C implementation.

Previously this function was injected at build time via a patch script
in the wasm-udf-server repository. Moving it into the source tree is a
prerequisite for cleaning up the custom componentize-py builder and
simplifying the WASM component build process.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: kesmit13