e2e: enable the egressauthz suite and delete sdsmint suite

[haiyanmeng]

The old sdsmint suite includes three tests: TestSdsmintMintsALeafPerSN,
TestGatewayRefusesANonActorWorkload and TestGatewayRefusesAnUnknownActor.

The egressmitm suite covers the e2e functionality of sdsmint, making
TestSdsmintMintsALeafPerSNI unnecessary.

TestGatewayRefusesANonActorWorkload and TestGatewayRefusesAnUnknownActor
used to live in the sdsmint suite. But their functionality does not
depend on sdsmint. So move them into a suite egressauthz.

New manifest_test.go verifies that the MITM CA is only mounted
on the `sdsmint` container in the `atenet-egress` Deployment.

The new egressauthz test suite takes about 13s to finish:

Phase	Δ	Cumulative
Framework init → Creating namespace	1.45s	1.45s
Namespace created, unknown-actor credential minted	0.31s	1.76s
ko build	3.05s	4.81s
ko publish to GCR	1.92s	6.73s
kubectl apply → pod created	3.42s	10.15s
Pod scheduled, image pulled, ready	2.36s	12.51s
TestGatewayRefusesANonActorWorkload	0.49s	13.00s
TestGatewayRefusesAnUnknownActor	0.05s	13.05s

It's a good idea to open an issue first for discussion.

• Tests pass
• Appropriate changes to documentation are included in the PR

[haiyanmeng]

Note for reviewers: Most of the code in this file is from the deleted file internal/e2e/suites/sdsmint/sdsmint_test.go.