bump rustler to 0.35.0 failed

[takasehideki]

We have been slacking a lot on updating our dependent library packages/libraries, so I have been working on this with the help of dependabot. Also, I have added cargo packages as the target to be updated automatically by dependabot (see #62). This will also work fine for proper correspondence between mix and cargo.

As a result, #67 tries to bump rustler in Cargo.toml significantly, from 0.32.1 to 0.35.0.
This has led to the discovery of issues whereby existing sources cannot be built. We need to look step by step to see what the cause is.

Related info:
https://hexdocs.pm/rustler/upgrade.html#content

[takasehideki]

#69 has bumped Rustler to 0.34.0, not 0.35.0. IOW, this issue was not resolved.
We found that Rustler 0.35.0 with Zenoh 0.11.0 caused many inexplicable compile errors. I guess that these are probably due to that the transition from async-std to Tokio was not yet complete in Zenoh 0.11.0. I have experimentally tried Zenoh 1.0 along with Rustler 0.35.0; most of the errors seemed not appear at that time (although many other compile errors happened, so we will have to work on resolving them).

• mix_compile-Rustler0.35.0_Zenoh0.11.0.log
• mix_compile-Rustler0.35.0_Zenoh1.0.1.log

Therefore, we will try to bump Zenoh to 1.0 first, and then tackle this issue.