Invalid AIP linter for AIP-123 generates false positive findings.

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#### Environment details

- Programming language: protocol buffers
- OS: Any
- Language runtime version: Any
- Package version: Any

#### Steps to reproduce

1. Create a protocol buffer message with a string field called `name`.
2. Run AIP linter against it.
3. The linter will complain with the message "Resource messages should include a `google.api.resource` annotation. https://linter.aip.dev/123/resource-annotation"

#### Description of the issue
1. [AIP-123](https://google.aip.dev/123) says "APIs **should** annotate the resource types for each resource in the API using the `google.api.resource` annotation". It does not specify how the resource type can be identified automatically.
2. [AIP-122](https://google.aip.dev/122) says "Resources **must** expose a `name` field that contains its resource name."
3. [AIP-123 Linter](https://linter.aip.dev/123/resource-annotation#details) "(...) assumes that messages with a `string name` field are resources unless the message name ends with `Request`."

AIP-123 linter recognizes messages with `name` field as resources, which is prune to false positives (see AIP-123), e.g. one may have messages with `string name` field, which are not resources. Then the linter requires them to have `google.api.resource` annotation, which is a **should** requirement only.

Proposed changes:
- AIP-123 linter checks performs different checks, which are defined in the AIP-122:
- "Patterns **must** correspond to the `resource name`",
- "Pattern variables (the segments within braces) **must** use `snake_case`, and **must not** use an `_id` suffix."
- AIP-122 linter checks that all messages with a `google.api.resource` annotation, which are assumed to be resources, have a `string name` field. This is also a heuristic, but should generate fewer false-positive, as it requires presence of the annotation to assume the message is a resource.