[chip-test] chip_sw_alert_handler_lpg_sleep_mode_pings

Nobody has claimed this yet.

### Test point name

[chip_sw_alert_handler_lpg_sleep_mode_pings](https://github.com/lowRISC/opentitan/blob/3f65c2a534fc75ed43f3af438f01afc5232bfc2b/hw/top_earlgrey/data/ip/chip_alert_handler_testplan.hjson#L189-L211)

### Host side component

None

### OpenTitanTool infrastructure implemented

None

### Silicon Validation (SiVal)

Yes

### Emulation Targets

- [ ] None
- [X] CW310
- [ ] Hyperdebug + CW310

### Contact person

@msfschaffner

### Checklist

Please fill out this checklist as items are completed. Link to PRs and issues as appropriate.
- [ ] Check if existing test covers most or all of this testpoint (if so, either extend said test to cover all points, or skip the next 3 checkboxes)
- [ ] Device-side (C) component developed
- [ ] Bazel build rules developed
- [ ] Host-side component developed
- [ ] HJSON test plan updated with test name (so it shows up in the dashboard)
- [ ] Test added to dvsim nightly regression (and passing at time of checking)
- [ ] For SiVal test cases, test is running relevant FPGA or silicon regression

> estimate 0.5

Start with the chip_sw_alert_handler_lpg_sleep_mode_pings entry in hw/top_earlgrey/data/ip/chip_alert_handler_testplan.hjson. Review the existing checklist and related test coverage, then determine the device-side component, Bazel rules, HJSON test-plan update, and CW310 regression steps needed. Done means the test is implemented and passing in the relevant regression.

Written by the indexing model from the issue text.