Add `textual_hdrs` to cc_binary

### Description of the feature request:

Given that there is an allowlist of possible file extensions in `hdrs=` and that `cc_binary` doesn't have a `textual_hdrs` attribute, there isn't really a good way to say "this `cc_binary` has a source file that is included from somewhere but it doesn't compile by itself".

Sounds like a logical addition and nice polish.

### Which category does this issue belong to?

C++/Objective-C Rules

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

_No response_

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

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

_No response_

### 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?

_No response_

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

_No response_

Start at the cc_binary rule and the existing hdrs attribute allowlist; the issue does not name implementation files or tests. Determine how textual_hdrs should be represented for cc_binary, then add coverage showing that a source included elsewhere is accepted without compiling independently.

Written by the indexing model from the issue text.