Return error if provided config was missing or invalid

[banool]

Description

Currently if you pass in an explicit config path but there is no file at the path, or the config is missing, it just silently continues without even a warning. This PR makes it return an error in this case.

Test Plan

cargo run --release -p aptos -- node run-local-testnet --force-restart --config-path /tmp/does_not_exist.yaml --assume-yes

Output (when this PR is on top of https://github.com/aptos-labs/aptos-core/pull/5261):

Node stopped unexpectedly Err(
    Error {
        context: "Failed to load config at path: \"/tmp/does_not_exist.yaml\"",
        source: Unexpected(
            "Failed to open config file: \"/tmp/does_not_exist.yaml\". Error: Os { code: 2, kind: NotFound, message: \"No such file or directory\" }",
        ),
    },
)
{
  "Error": "Unexpected error: One of the components stopped unexpectedly"
}

I checked and didn't see any location where we depend on the bad current behavior in our deployment code, and the CI will let us know if forge does.

---

This change is 

[github-actions[bot]]

Forge is running suite land_blocking on 71ab416eca330e39074f7e0736dcaccbd4cec5c3

• Grafana dashboard (auto-refresh)
• Humio Logs
• Test runner output
• Test run is land-blocking

[github-actions[bot]]

Forge is running suite compat on 2d8b1b57553d869190f61df1aaf7f31a8fc19a7b ==> 71ab416eca330e39074f7e0736dcaccbd4cec5c3

• Grafana dashboard (auto-refresh)
• Humio Logs
• Test runner output
• Test run is land-blocking

[github-actions[bot]]

:white_check_mark: Forge suite compat success on 2d8b1b57553d869190f61df1aaf7f31a8fc19a7b ==> 71ab416eca330e39074f7e0736dcaccbd4cec5c3

Compatibility test results for 2d8b1b57553d869190f61df1aaf7f31a8fc19a7b ==> 71ab416eca330e39074f7e0736dcaccbd4cec5c3 (PR)
1. Check liveness of validators at old version: 2d8b1b57553d869190f61df1aaf7f31a8fc19a7b
compatibility::simple-validator-upgrade::liveness-check : 7599 TPS, 5109 ms latency, 6800 ms p99 latency,no expired txns
2. Upgrading first Validator to new version: 71ab416eca330e39074f7e0736dcaccbd4cec5c3
compatibility::simple-validator-upgrade::single-validator-upgrade : 4898 TPS, 8330 ms latency, 11400 ms p99 latency,no expired txns
3. Upgrading rest of first batch to new version: 71ab416eca330e39074f7e0736dcaccbd4cec5c3
compatibility::simple-validator-upgrade::half-validator-upgrade : 4541 TPS, 9241 ms latency, 11300 ms p99 latency,no expired txns
4. upgrading second batch to new version: 71ab416eca330e39074f7e0736dcaccbd4cec5c3
compatibility::simple-validator-upgrade::rest-validator-upgrade : 6542 TPS, 5844 ms latency, 10700 ms p99 latency,no expired txns
5. check swarm health
Compatibility test for 2d8b1b57553d869190f61df1aaf7f31a8fc19a7b ==> 71ab416eca330e39074f7e0736dcaccbd4cec5c3 passed
Test Ok

• Grafana dashboard
• Humio Logs
• Test runner output
• Test run is land-blocking

[github-actions[bot]]

:white_check_mark: Forge suite land_blocking success on 71ab416eca330e39074f7e0736dcaccbd4cec5c3

performance benchmark with full nodes : 6866 TPS, 5788 ms latency, 8800 ms p99 latency,no expired txns
Test Ok

• Grafana dashboard
• Humio Logs
• Test runner output
• Test run is land-blocking