Add support for actor upgrades (#1866)

This PR adds support for actor upgrades through a new `sdk::actor::upgrade_actor` syscall. This allows actors to upgrade to a new version while still keeping the same address, balance, etc.

Instead of introducing a separate syscall to fetch `get_old_code_cid` this PR implements the alternative where we pass a upgrade metadata to the upgrade endpoint as proposed [here](filecoin-project/FIPs#396 (comment)).

fixes #171

fvm/Cargo.toml

@@ -66,4 +66,5 @@ cuda-supraseal = ["filecoin-proofs-api/cuda-supraseal"]
 testing = []
 arb = ["arbitrary", "quickcheck", "fvm_shared/arb", "cid/arb"]
 m2-native = []
+upgrade-actor = []
 gas_calibration = []

fvm/src/call_manager/backtrace.rs

@@ -4,10 +4,12 @@ use std::fmt::Display;
 
 use fvm_shared::address::Address;
 use fvm_shared::error::{ErrorNumber, ExitCode};
-use fvm_shared::{ActorID, MethodNum};
+use fvm_shared::ActorID;
 
 use crate::kernel::SyscallError;
 
+use super::Entrypoint;
+
 /// A call backtrace records the actors an error was propagated through, from
 /// the moment it was emitted. The original error is the _cause_. Backtraces are
 /// useful for identifying the root cause of an error.
@@ -76,8 +78,8 @@ impl Backtrace {
 pub struct Frame {
     /// The actor that exited with this code.
     pub source: ActorID,
-    /// The method that was invoked.
-    pub method: MethodNum,
+    /// The entrypoint that was invoked.
+    pub entrypoint: Entrypoint,
     /// The exit code.
     pub code: ExitCode,
     /// The abort message.
@@ -90,7 +92,7 @@ impl Display for Frame {
             f,
             "{} (method {}) -- {} ({})",
             Address::new_id(self.source),
-            self.method,
+            self.entrypoint,
             &self.message,
             self.code,
         )