Bump rust build image to 1.70

[andrei-21]

Recent version of tokio requires at least rust 1.70

package tokio v1.44.2 cannot be built because it requires rustc 1.70 or newer, while the currently active rustc version is 1.64.0

[TheBlueMatt]

This crate doesn't depend on any features in the new tokio, however, so we should instead pin tokio and then it'll build fine.

[andrei-21]

I managed to fix it, but I had to pin tokio to 1.35, because lightning-net-tokio requires it:

error: failed to select a version for `tokio`.
    ... required by package `lightning-net-tokio v0.1.0`
    ... which satisfies dependency `lightning-net-tokio = "^0.1.0"` of package `rapid-gossip-sync-server v0.1.0 (/home/an/pr/andrei-21/ldk/rapid-gossip-sync-server)`
versions that meet the requirements `^1.35` are: 1.35.1, 1.44.2, 1.44.1, 1.44.0, 1.43.1, 1.43.0, 1.42.1, 1.42.0, 1.41.1, 1.41.0, 1.40.0, 1.39.3, 1.39.2, 1.39.1, 1.38.2, 1.38.1, 1.38.0, 1.37.0, 1.36.0, 1.35.0

And pin postgres-types to 0.2.6 because newer version are not compatible with Rust 1.64:

    Checking postgres-types v0.2.9
error[E0658]: `let...else` statements are unstable
  --> /home/an/.cargo/registry/src/github.com-1ecc6299db9ec823/postgres-types-0.2.9/src/pg_lsn.rs:36:9
   |
36 | /         let Some((split_hi, split_lo)) = lsn_str.split_once('/') else {
37 | |             return Err(ParseLsnError(()));
38 | |         };
   | |__________^

Does it worth it or it is simpler to bump the Rust version?

[TheBlueMatt]

Ah, yea, I guess for the docker file its fine to just bump rustc. We still support older rustc in the builds but via pins.