Support modern package_manager mode

[uilianries]

Description of Problem, Request, or Question

So far, CONAN_SYSREQUIRES_MODE is the environment variable which rules the legacy SystemPackageTool, however, with the migration of recipe and modernization of package manager support, the conan.tools.system.package_manager uses config to enable installing by default.

As current workaround, need to run script before to build on Docker to enable it, updating the global config file.

The feature consists updating it automatically, by adding a new cpt option, which will update both legacy and modern version. For instance:

CPT_SYSREQUIRES_MODE=[install, check, disable]

• install: equivalent to CONAN_SYSREQUIRES_MODE=enabled + tools.system.package_manager:mode=install
• check: equivalent to CONAN_SYSREQUIRES_MODE=verify + tools.system.package_manager:mode=check
• disabled: equivalent to CONAN_SYSREQUIRES_MODE=disabled + tools.system.package_manager:mode=None (It should accept False and None too)

CONAN_SYSREQUIRES_SUDO=[true,false]

• true, 1, yes: Uses sudo command to execute the system package manager tool
• false, 0, no: Do not use sudo command to execute the system package manager tool

CONAN_SYSREQUIRES_TOOL=[apt-get, yum, dnf, brew, pacman, choco, zypper, pkg, pkgutil]

It follows those supported tools listed on modern system package

[SSE4]

I would prefer some generic feature allowing to set arbitrary conf variables on command line. then, build tools.system.package_manager:mode on top of it.

[uilianries]

@SSE4 Yes, it sounds even better.