R1:433a7321ff25

Add harbormaster.buildable.search API Method

Summary:
This revision adds a Conduit search method for buildables. It exposes:
* `objectPHID`
* `containerPHID`
* `buildableStatus`
* `isManual`

Test Plan:
Use the API Console to run searches. Example:
```
{
"data": [
{
"id": 2,
"type": "HMBB",
"phid": "PHID-HMBB-m4k5lodx6naq22576a7d",
"fields": {
"objectPHID": "PHID-DIFF-vzvgqqcyscpd7ta4osy2",
"containerPHID": "PHID-DREV-vsivs5276c7vtgpmssn2"…