Support the new(ish) `@//tools/cpp:cc_runtimes_toolchain_type` toolchain for adding runtimes-on-demand.
* Add `get_cc_runtimes` and `get_cc_runtimes_copts` implementations to `cc_helper[_internal]`.
* TODO update usage in `rules_python` and others to call `cc_helper` and deprecate `semantics.get_cc_runtimes*`

Basic Usage:

Define a provider like:
```
CcRuntimesInfo = provider(
    doc = "Information about runtime libraries to link into c++ targets.",
    fields = ["runtimes", "copts"],
)
```

Define a toolchain that returns that provider:
```
def _cc_runtimes_toolchain_impl(ctx):
    return [platform_common.ToolchainInfo(
        cc_runtimes_info = CcRuntimesInfo(
            runtimes = ctx.attr.runtimes,
            copts = ctx.attr.copts,
        ),
    )]
```
* `runtimes` is a collection of CcInfo providing targets
* `copts` provides compilation flags that must be used alongside this toolchain, e.g. to influence include ordering.

This may be used, e.g. in rules_android_ndk: https://github.com/bazelbuild/rules_android_ndk/issues/93

PiperOrigin-RevId: 941244580
Change-Id: I31bade595714dbe44aa0d70afaa97ddd788e5635