AIP-123: Alternating collection identifiers and singletons

I believe that this PR introduced a bug: https://github.com/googleapis/api-linter/pull/1151

As stated in AIP-122:

> Resource name components should usually alternate between collection identifiers (example: publishers, books, users) and resource IDs (example: 123, les-miserables, vhugo1802).

Note the word "usually"

As stated in AIP-156:

> Singleton resources **may** parent other resources.

And...

> Singleton resources **must not** have a user-provided or system-generated ID; their [resource name][aip-122] includes the name of their parent followed by one static-segment.

While, this is not explicit in the documentation, I would expect the singleton pattern, with the ability to be a parent of other resources, to take precedent and put "usually" to the test.

(very contrived) Example of the problem:

```proto
// Each user can only have a single library
message Library {
// The pattern indicates that a user is the canonical parent for library
option (google.api.resource) = {
type: "library.googleapis.com/Library"
pattern: "users/{user}/library"
singular: "library"
plural: "libraries"
};

// The resource name for the user's library
// Format: "users/{user}/library"
string name = 1 [(google.api.field_behavior) = IDENTIFIER];

// Resource names for books in the library
// Format: "users/{user}/library/books/{book}
repeated string books = 2 [
(google.api.resource_reference) = {type: "library.googleapis.com/Book"},
(google.api.field_behavior) = REQUIRED
];
}

// Each user's library can have many books
// (-- api-linter: core::0123::resource-name-components-alternate=disabled
// aip.dev/not-precedent: sad panda --)
message Book {
// The pattern indicates that a library is the canonical parent for book
option (google.api.resource) = {
type: "library.googleapis.com/Book"
pattern: "users/{user}/library/books/{book}"
singular: "book"
plural: "books"
};

// The resource name for the book in a user's library
// Format: "users/{user}/library/books/{book}"
string name = 1 [(google.api.field_behavior) = IDENTIFIER]
}
```

Curious to hear your thoughts?