Add support for UCS-2 strings

[nariman]

Trying to fix an issue, when py-spy would not parse a stack trace containing functions with cyrillic names.

py-spy/src/python_data_access.rs

Lines 26 to 31 in 4a11c44

	(2, _) => {
	// UCS2 strings aren't used internally after v3.3: https://www.python.org/dev/peps/pep-0393/
	// TODO: however with python 2.7 they could be added with --enable-unicode=ucs2 configure flag.
	// or with python 3.2 --with-wide-unicode=ucs2
	Err(format_err!("ucs2 strings aren't supported yet!"))
	},

Seems like UCS-2 strings are in use by some (maybe all?) pre-built Python binaries (tested on mcr.microsoft.com/devcontainers/rust:1-1-bullseye Dev Container, our company's CentOS environment, as well as my local environment with Python 3.7 and 3.11 versions installed using pyenv).

If there's a function with a UCS-2 encoded name on the first recorded stack trace, py-spy just fails.

Example

import time

def кириллица(seconds):
    time.sleep(seconds)

if __name__ == "__main__":
    кириллица(10)

Outputs (profile.svg will not be created in this case):

$ py-spy record -o profile.svg -- python3 tests/scripts/cyrillic.py 
Error: Failed to find a python interpreter in the .data section

If py-spy successfully started the recorder, we'll get a flamegraph built without stack traces with UCS-2 strings, so final data/graph will look strange or even misleading.

Example

import time

def function1(seconds):
    time.sleep(seconds)

def кириллица(seconds):
    time.sleep(seconds)

if __name__ == "__main__":
    function1(10)
    кириллица(10)

Outputs (profile.svg will be created):

$ py-spy record -o profile.svg -- python3 tests/scripts/cyrillic.py 
py-spy> Sampling process 100 times a second. Press Control-C to exit.


py-spy> Stopped sampling because process exited
py-spy> Wrote flamegraph data to 'profile.svg'. Samples: 12 Errors: 1025

[benfred]

thanks for the change!