Feature flags for common compiler options (e.g. C++ standard)

### Description of the problem / feature request:

Allow customizing common flags (e.g. standard version) via features.

### Feature requests: what underlying problem are you trying to solve with this feature?

I want to not add compiler dependent flags to .bazelrc nor to my rules. Instead, I believe some of the common options (e.g. --std=c++17) could be best modelled by features. Moreover, this would add clear documentation w.r.t. what's the default standard on each toolchain as opposed to being hardcoded (https://github.com/bazelbuild/rules_cc/search?q=%22-std%3Dc%2B%2B%22).

### Have you found anything relevant by searching the web?

- https://stackoverflow.com/questions/40260242/how-to-set-c-standard-version-when-build-with-bazel

The issue names no files, tests, or entry points. Begin by reviewing how rules_cc models compiler options and the linked C++ standard discussion, then define which common flags should become features and document defaults per toolchain.

Written by the indexing model from the issue text.