Conan 1.x: Fix VCVars for Clang with v14.4 toolset

[glebov-andrey]

Changelog: Bugfix: Fix LLVM/Clang enablement of vcvars for latest v14.4 toolset version after VS 17.10 update
Docs: conan-io/docs#3830

Close #16930

Partially backports #16374. The tools.microsoft:msvc_update conf property is not present in Conan 1 so its usage is omitted.
This change should not break any existing users because it only adds code paths which run when the compiler.runtime_version setting is updated to v144, only for clang and only in the VCVars generator.

• Refer to the issue that supports 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.

[CLAassistant]

All committers have signed the CLA.

[memsharded]

I think this should be very low risk, so no problem with merging this for next Conan 1.66

[memsharded]

There is a test that is failing:

conans/test/integration/test_migrations.py::TestMigrations::test_migrations_matches_config

This test checks the migration is working fine.
To fix it is necessary to change the migration_settings.py final settings_1_66_0 = settings_1_65_0 and define
settings_1_66_0 = <full new settings yaml including the new values.

This is an inconvenient way of updating the settings.yml in Conan 1.X, fortunately this was improved in Conan 2 and such migrations are fully automatic.

[czoido]

There is a test that is failing:

conans/test/integration/test_migrations.py::TestMigrations::test_migrations_matches_config

This test checks the migration is working fine. To fix it is necessary to change the migration_settings.py final settings_1_66_0 = settings_1_65_0 and define settings_1_66_0 = <full new settings yaml including the new values.

This is an inconvenient way of updating the settings.yml in Conan 1.X, fortunately this was improved in Conan 2 and such migrations are fully automatic.

I have just fixed it, it should pass now