Provide Starlark analogue to "rlocationpath" Make variable for rule authors to use

### Description of the feature request:

Per [discussion in the "rules" channel](https://bazelbuild.slack.com/archives/CDCMRLS23/p1674078669014879) of the "Bazel" Slack workspace, at present we have [the `rlocationpath` "Make" variable](https://bazel.build/reference/be/make-variables) available for use in target definitions, but we have no analogous Starlark function available to rule authors. It would be helpful to provide either a Starlark function that accepts a `File` or add a method to `File` that returns the equivalent string value as the `rlocationpath` "Make" variable, such that one could feed that value into a runfiles library's `Rlocation` function to find a particular runfile.

### What underlying problem are you trying to solve with this feature?

While writing a rule that externalizes command-line flags or arguments supplied to an action created by `ctx.actions.run` or `ctx.actions.run_shell`, I'd like to supply values that nominate runfiles, such that the program that runs within that action can use a runfiles library to project those command-line flag values to the proper paths, allowing it to read the nominated files.

### Which operating system are you running Bazel on?

macOS 13.1

### What is the output of `bazel info release`?

release 6.0.0

### If `bazel info release` returns `development version` or `(@non-git)`, tell us how you built Bazel.

_No response_

### What's the output of `git remote get-url origin; git rev-parse master; git rev-parse HEAD` ?

_No response_

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

I have searched the Web extensively looking for advice on how to use the nascent runfiles libraries. @fmeum's ["Runfiles and where to find them" video on YouTube](https://www.youtube.com/watch?v=5NbgUMH1OGo) helps understand how to _consume_ these paths. Not addressed commonly, though, is how one _creates_ these paths.

### Any other information, logs, or outputs that you want to share?

@fmeum [mentioned](https://bazelbuild.slack.com/archives/CDCMRLS23/p1674111770913389?thread_ts=1674078669.014879&cid=CDCMRLS23) his [`runfile_path` Starlark function](https://github.com/bazelbuild/rules_fuzzing/blob/22a866a3c98f374ab3284a7d26fc8318c17a711c/fuzzing/private/util.bzl#L39-L42) in the _bazelbuild/rules\_fuzzing_ repository as a potential implementation that emulates `rlocationpath` well enough.

Start with the documented rlocationpath Make variable and the rules_fuzzing runfile_path Starlark function linked in the issue. Review how rule authors use File values with ctx.actions.run and ctx.actions.run_shell, and how runfiles libraries consume Rlocation inputs. Done means rule authors can obtain an equivalent runfile path for an action argument.

Written by the indexing model from the issue text.