wifi: Changes to WifiLegacy Hal

Changes in the CL:
a. Removed the usage of wifi_status_util in WifiLegacyHal. The
|legacyErrorToString| log will be done in the HIDL object. This is to
remove any reference of |WifiStatus|
b. Moved the cleanup of function pointers to a separate helper function
|invalidate|.
c. Moved static constants out of WifiLegacyHal class.

Bug: 32505551
Test: Compiles
Change-Id: I9dc3900c40cf30de2c0a4376d4de2b08076e2b5f