[AWS::DocDB::DBCluster] - [Coverage] - Add support for stack drift detection

### Name of the resource

AWS::DocDB::DBCluster

### Resource name

AWS::DocDB::DBCluster, AWS::DocDB::DBInstance, AWS::DocDB::DBClusterParameterGroup

### Description

`AWS::DocDB::DBCluster`, `AWS::DocDB::DBInstance`, and `AWS::DocDB::DBClusterParameterGroup` are entirely absent from CloudFormation's [resource support table](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/resource-import-supported-resources.html) — not listed as supported, not listed as unsupported, just not present at all (verified directly against the raw documentation source; other resource types like `AWS::RDS::DBCluster` and `AWS::S3::Bucket` are correctly present with real Yes/No columns). This means these resource types aren't yet part of the Cloud Control API-based framework that provides drift detection (and import).

Practical consequence: `detect-stack-drift` silently omits these resources from its "Resource drift status" results — with only a small console caption noting that unsupported resources are hidden — while the stack's overall drift status still reports `IN_SYNC`, giving a false impression that the stack has no drift. The same limitation appears on the newer drift-aware change sets (`--deployment-mode REVERT_DRIFT`), which explicitly return `"ResourceDriftStatus": "UNSUPPORTED"` for these same resource types.

Concretely: a stack had `EngineVersion: 4.0.0` in its template while the live DocumentDB cluster had been upgraded outside CloudFormation to `5.0.0`. This real, significant drift was completely invisible to both `detect-stack-drift` and drift-aware change sets — not because either tool checked and found no difference, but because these resource types aren't evaluated at all.

**Request:** Add `AWS::DocDB::DBCluster`, `AWS::DocDB::DBInstance`, and `AWS::DocDB::DBClusterParameterGroup` to CloudFormation's resource coverage for stack drift detection (ideally alongside import support, since #2339 already separately requests import for `DBCluster`).

### Other Details

Verified directly against the raw source of [resource-import-supported-resources.md](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/resource-import-supported-resources.html) — zero `docdb` matches. Related open issues: #2339 (Import support for `AWS::DocDB::DBCluster` — same underlying gap, Import specifically); #1858 / #2283 (similar "`IN_SYNC` but actually drifted" symptom for other resource types, though those involve undetected property changes on resources that *are* covered, rather than resource types missing from coverage entirely).

Start with the raw resource-import-supported-resources.md source linked in the issue and compare the existing entries for AWS::RDS::DBCluster and AWS::S3::Bucket. Review related issues #2339, #1858, and #2283 for scope and prior discussion. Done means the three AWS::DocDB resource types are covered by stack drift detection and no longer report UNSUPPORTED in drift-aware change sets.

Written by the indexing model from the issue text.