Rust 1.81 was released and comes with a load of niceties that we would like to use. Among them of immediate interest are:

1. lint reasons (Replace all allow attributes by expect and require lint reasons #1521)
2. fixes clippy::blocks_in_conditions lint triggering on proc macros like tracing::instrument (which chore(sequencer): Add instrumentation #1368 needed to work around)
3. lazy lock and lazy cell (to replace once_cell) in 1.80 (Replace once_cell by sync primitives added in 1.80 #1520)
4. checked cfg names (also 1.80 which flags a few issues in our code and should be immediately available).

Note that this is orthgonal to setting the MSRV in individual Astria crates.

┆Issue Number: ENG-818