remove redundancy in node.config schema keys

What is the problem this feature will solve?

Notice below how in the current schema, the namespaces "test" and "watch" are redundantly specified. This is the result of mapping the CLI args as-is.

{
    "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
    "test": {
        "test-concurrency": 3
        "test-isolation": "process"
        "test-timeout": 5000
        "test-rerun-failures": true
        "test-only": true
        "test-force-exit": false
        "test-name-pattern": "^iso"
        "test-skip-pattern": "tree$"
        "test-global-setup": "setup-module.mjs"
        "experimental-test-coverage": true
        "test-coverage-exclude": "test/**"
        "test-coverage-include": "src/**"
        "test-coverage-branches": 100
        "test-coverage-functions": 100
        "test-coverage-lines": 100
        "test-reporter": ["dot", "spec", "lcov"]
        "test-reporter-destination": ["stdout", "test.report", "lcov.info"]
        "experimental-test-module-mocks": true
        "test-update-snapshots": true
    },
    "watch": {
        "watch-preserve-output": true
        "watch-path": "./src"
    }
} 

What is the feature you are proposing to solve the problem?

Instead, the namespace part of the CLI arg could automatically be mapped to a namespace within the config schema:

{
    "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
    "test": {
        "concurrency": 3
        "isolation": "process"
        "timeout": 5000
        "rerun-failures": true
        "only": true
        "force-exit": false
        "name-pattern": "^iso"
        "skip-pattern": "tree$"
        "global-setup": "setup-module.mjs"
        "experimental-coverage": true
        "coverage-exclude": "test/**"
        "coverage-include": "src/**"
        "coverage-branches": 100
        "coverage-functions": 100
        "coverage-lines": 100
        "reporter": ["dot", "spec", "lcov"]
        "reporter-destination": ["stdout", "test.report", "lcov.info"]
        "experimental-module-mocks": true
        "test-update-snapshots": true
    },
    "watch": {
        "preserve-output": true
        "path": "./src"
    }
} 

Note that for "experimental-" CLI args, the mapped namespace occurs after that prefix.

We can take it a step further, apply the idea recursively, as below. This has the added of benefit fixing how destinations are specified when there are multiple test reporters.

{
    "$schema": "https://nodejs.org/dist/vX.Y.Z/docs/node-config-schema.json",
    "test": {
        "concurrency": 3
        "isolation": "process"
        "timeout": 5000
        "rerun-failures": true
        "only": true
        "force-exit": false
        "name-pattern": "^iso"
        "skip-pattern": "tree$"
        "global-setup": "setup-module.mjs"
        "experimental-coverage": {
            "exclude": "test/**"
            "include": "src/**"
            "branches": 100
            "functions": 100
            "lines": 100
        }
        "reporter": {
            "dot": {"destination": "stdout"}
            "spec": {"destination": "test.report"}
            "lcov": {"destination": "lcov.info"}
        }
        "experimental-module-mocks": true
        "update-snapshots": true
    },
    "watch": {
        "preserve-output": true
        "path": "./src"
    }
} 

What alternatives have you considered?

No response

Start by tracing Node's CLI-argument-to-config-schema mapping and compare how the current test and watch keys are generated. The issue's examples define the intended result: namespace prefixes should be removed, experimental options handled after their prefix, and nested reporter destinations mapped recursively.