fix: check trunkENI attached status if it already exists before adding to cache

[sushrk]

Issue #, if available:
#209
Description of changes:

1. Check attached status if the trunkENI exists before adding to cache to avoid the leaked ENI breaking SGPP communication.
2. Refactored InitTrunk test case to use table-driven test cases
3. Bump gomega and update developer guide

Testing

SGPP tests
Ran 19 of 23 Specs in 1732.780 seconds
FAIL! -- 18 Passed | 1 Failed | 0 Pending | 4 Skipped

Webhook tests
Ran 11 of 11 Specs in 146.382 seconds
SUCCESS! -- 11 Passed | 0 Failed | 0 Pending | 0 Skipped

Known failure fixed in commit ba8963a, re-ran with focus-

Branch ENI Pods Toggle Node between Managed/Un-Managed when node is toggled from managed to un-managed and back to managed pod should not run when un-managed and run when managed

Ran 1 of 23 Specs in 546.345 seconds
SUCCESS! -- 1 Passed | 0 Failed | 0 Pending | 22 Skipped

Ran scale up/down tests with upto 50 nodes and 100 pods and verified branch & trunkeni is allocated and deleted as expected.

{"level":"info","timestamp":"2023-08-10T20:59:41.269Z","logger":"branch eni provider","msg":"created and annotated branch interface/s successfully","pod namespace":"default","pod name":"hello-world-7db65f56dd-xg6vt","node name":"XX","branches":[{"eniId":"eni-XX","ifAddress":"XX","privateIp":"XX","vlanId":X,"subnetCidr":"XX"}]}
{"level":"info","timestamp":"2023-08-10T21:07:05.003Z","logger":"branch eni provider","msg":"pushing ENIs to delete queue","node name":"XX","ENIs":[{"eniId":"eni-XX","ifAddress":"XX","privateIp":"XX","vlanId":X,"subnetCidr":"XX"}]}

{"level":"info","timestamp":"2023-08-10T20:59:33.123Z","logger":"branch eni provider","msg":"trunk added to cache successfully","node":"XX"}
{"level":"info","timestamp":"2023-08-10T21:11:16.003Z","logger":"node manager","msg":"node removed from data store","node name":"XX","request":"delete"}
{"level":"info","timestamp":"2023-08-10T20:35:21.971Z","logger":"branch eni provider","msg":"trunk removed from cache successfully","node":"XX"}

{"level":"info","timestamp":"2023-08-10T21:17:47.428Z","logger":"branch eni provider","msg":"trunk removed from cache successfully","node":"XX"}
{"level":"info","timestamp":"2023-08-10T21:17:47.428Z","logger":"branch eni provider","msg":"de-initialized resource provider successfully","node name":"XX"}

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[haouc]

lgtm