Items resolved:
1. fix the vet error: possible misuse of reflect.SliceHeader;
2. fix the vet error: call to (*T).Fatal from a non-test goroutine;
3. bump package golang.org/x/crypto, net and sys;
4. bump boltdb from 1.3.3 to 1.3.6;
5. remove the vendor directory;
6. remove go 1.12.17 and 1.15.15, add go 1.16.15 into pipeline;
7. bump go version to 1.16 in go.mod;
8. fix the issue: compile: version go1.16.15 does not match go tool version go1.17.11,
refer to https://github.com/actions/setup-go/issues/107;
9. fix data race on compactMainRev and watcherGauge;
10. fix test failure for TestLeasingTxnOwnerGet in cluster_proxy mode.
Signed-off-by: Benjamin Wang <wachao@vmware.com>
