[fix] CONAN_TOOLCHAIN_ARGS_FILE as configuration file

[franramirez688]

Changelog: Fix: Saving all the toolchain args information into conanbuild.conf instead of json file.
Docs: conan-io/docs#2156

• Saving all the toolchain args information into conanbuild.conf.
• Using a default configuration section called toolchain.
• Using ConfigParser as internal mechanism to manage the load and saving of the toolchain-file content.

Closes #9130

• Refer to the issue that supports this Pull Request.
• If the issue has missing info, explain the purpose/use case/pain/need that covers this Pull Request.
• I've read the Contributing guide.
• I've followed the PEP8 style guides for Python code.
• I've opened another PR in the Conan docs repo to the develop branch, documenting this one.

^{Note: By default this PR will skip the slower tests and will use a limited set of python versions. Check here how to increase the testing level by writing some tags in the current PR body text.}

[memsharded]

Looking good so far, please check comments.