Get max drive size cloudops interface

[ppadalia]

root@diags:~/git/go/src/github.com/libopenstorage/cloudops# make
go build -tags ""  ./...
go vet ./...

root@diags:~/git/go/src/github.com/libopenstorage/cloudops# grep -snr maxDriveSize ~/test_out
631:=== RUN   TestAWSStorageManager/maxDriveSize
644:    --- PASS: TestAWSStorageManager/maxDriveSize (0.00s)
840:=== RUN   TestAzureStorageManager/maxDriveSize
859:    --- PASS: TestAzureStorageManager/maxDriveSize (0.00s)
1179:=== RUN   TestGCEStorageManager/maxDriveSize
1194:    --- PASS: TestGCEStorageManager/maxDriveSize (0.00s)
1395:=== RUN   TestOracleStorageManager/maxDriveSize
1430:    --- PASS: TestOracleStorageManager/maxDriveSize (0.01s)
1547:=== RUN   TestVsphereStorageManager/maxDriveSize
1562:    --- PASS: TestVsphereStorageManager/maxDriveSize (0.00s)

What this PR does / why we need it: Add new interface to get max drive size for all clouds. For Pure, implementation is in porx and will be through different PR. For IBM, implementation is in csi.go

Which issue(s) this PR fixes (optional) Closes PWX-37215 Closes PWX-37118

Special notes for your reviewer: For Pure, implementation is in porx and will be added through different PR. For IBM, implementation is in csi.go

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 48.64865% with 19 lines in your changes are missing coverage. Please review.

Project coverage is 8.34%. Comparing base (f78dd2f) to head (fab0505).

Files	Patch %	Lines
pkg/storagedistribution/storagedistribution.go	0.00%	19 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #166 +/- ## ========================================= + Coverage 8.03% 8.34% +0.31% ========================================= Files 18 18 Lines 4756 4793 +37 ========================================= + Hits 382 400 +18 - Misses 4352 4371 +19 Partials 22 22 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.