Drop use of github.com/gorilla/mux #1380

Job	Run time
build-arm64 / Build	6m 31s
Build Go Tests (arm64)	3m 1s
Build Go Tests (amd64)	4m 2s
build / Build	8m 18s
E2E Tests (privateregistry)	7m 25s
E2E Tests (s3)	10m 51s
E2E Tests (rootless)	7m 9s
E2E Tests (startup)	15m 13s
E2E Tests (multus)	7m 19s
E2E Tests (btrfs)	7m 4s
E2E Tests (embeddedmirror)	8m 0s
E2E Tests (externalip)	7m 16s
E2E Tests (wasm)	6m 35s
Docker (bootstraptoken, arm64)	1m 51s
Docker (autoimport, amd64)	3m 35s
Docker (basics, arm64)	2m 12s
Docker (cacerts, arm64)	1m 57s
Docker (bootstraptoken, amd64)	3m 5s
Docker (svcpoliciesandfirewall, amd64)	3m 37s
Docker (lazypull, arm64)	2m 8s
Docker (basics, amd64)	2m 4s
Docker (etcd, amd64)	4m 10s
Docker (upgrade, arm64)	4m 4s
Docker (token, arm64)	4m 47s
Docker (cacerts, amd64)	2m 29s
Docker (snapshotrestore, amd64)	6m 32s
Docker (token, amd64)	4m 59s
Docker (nixsnapshotter, amd64)	3m 25s
Docker (lazypull, amd64)	2m 28s
Docker (hardened, amd64)	2m 49s
Docker (secretsencryption, amd64)	8m 9s
Docker (hardened, arm64)	3m 5s
Docker (upgrade, amd64)	4m 13s
Docker (etcd, arm64)	3m 55s
Docker (skew, arm64)	3m 9s
Docker (dualstack, amd64)	7m 43s
Docker (skew, amd64)	3m 59s
	3h 9m 9s

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