Add Stale Status Timestamp Check

[shahneerali]

When reading the GPA status.json file, it compares the GPA Version, we also need GPA VMExtension to check GPA status reported time. This is to report GPA is running or not and the status file up-to-date. Two scenarios could be detected by this improvement:

1. GPA service was down, hopefully it is in audit mode for WS. GPA VMExtension could report it (TBD report warning in subStatus)
2. When the cx re-opt-in MSP feature with GPA VMExtension, the VM Extension should ignore the stale status.josn file.

[ZhidongPeng]

Let's use the similar logic as version check, then we could share most of the code.

implemented suggestion

implemented suggestions