[release-1.15] fix(gateway): harden bfdd control operations

[zhangzujian]

What changed

• backport fix(gateway): prevent probe disconnects from restarting bfdd #7135, fix(gateway): bound bfdd control requests #7136, and fix(gateway): bound bfdd status operations #7137 in merge order
• keep the final OpenBFDD control-hardening patch identical to the merged master version
• adapt the readiness timeout and regression assertions to the release-1.15 VPC egress gateway file layout

Validation

• GOMAXPROCS=2 go test -p 1 ./pkg/controller -run '^(TestVpcEgressGatewayContainerBFDDDefaultResources|TestOpenBFDDControlHardeningPatch|TestBFDDHealthcheck)$' -count=1
• git diff --check origin/release-1.15...HEAD
• gofmt -d pkg/controller/vpc_egress_gateway_test.go
• applied the OpenBFDD compile and control-hardening patches to pinned OpenBFDD e35f43ad8d2b3f084e96a84c392528a90d05a287; configure completed successfully

The three commits retain their original Signed-off-by lines and cherry picked from trailers.