Add levels for handling spec validation via flag.

Replaces the flag "unsafe-skip-restore-spec-validation" with
"restore-spec-validation" which allows the user to set the level of restore
spec validation such as ignore, warning or enforce. This allows user to skip
validation if required. By default, the flag will be set to "enforce" which
will perform spec validation.

PiperOrigin-RevId: 713441769

runsc/boot/BUILD

@@ -133,6 +133,7 @@ go_library(
         "//runsc/profile",
         "//runsc/specutils",
         "//runsc/specutils/seccomp",
+        "//runsc/specvalidation",
         "//runsc/version",
         "@com_github_opencontainers_runtime_spec//specs-go:go_default_library",
         "@com_github_syndtr_gocapability//capability:go_default_library",