[fix] CONAN_TOOLCHAIN_ARGS_FILE as configuration file - #9225

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

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