Move from toml Python module to tomli

[dimakuv]

Description of the feature

Gramine and GSC use the toml Python package to parse and save TOML files.

This package is unfortunately buggy. One particularly nasty bug that GSC hit: gramineproject/gsc#101. This corresponds to this bug in the TOML repo: uiri/toml#404.

So Gramine and GSC should move to the tomli package (https://pypi.org/project/tomli/ and https://github.com/hukkin/tomli). It is newer, with better code quality, and seems to become a standard codebase for TOML parsing in Python:

A version of Tomli, the new tomllib module, will be added to the standard library in Python 3.11 via PEP 680. Tomli continues to provide a backport on PyPI for Python versions where the standard library module is not available and that have not yet reached their end-of-life.

(See https://github.com/hukkin/tomli#intro)

Why Gramine should implement it?

Because the old toml Python package is buggy. For example, we have to introduce this work around: gramineproject/gsc#101

[dimakuv]

Another bug in toml package: #990

[dimakuv]

I will work on moving to tomli Python package. As soon as this migration is done, I should:

1. Revert Work around TOML Python parser bug of parsing \x gsc#101 and check it still works.
2. Check that bug toml Python package v0.10.0 is buggy; need v0.10.2 #990 disappears and [LibOS,PAL] Add flexible device-specific IOCTL support #671 works.