Fix warnings for Rust 1.85.1 in libprefetch

```
error: `to_string` applied to a type that implements `Display` in `error!` args
   --> system/core/init/libprefetch/prefetch/src/replay.rs:153:38
    |
153 | ...                   e.to_string()
    |                        ^^^^^^^^^^^^ help: remove this
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_in_format_args
    = note: `-D clippy::to-string-in-format-args` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::to_string_in_format_args)]`

error: `to_string` applied to a type that implements `Display` in `warn!` args
   --> system/core/init/libprefetch/prefetch/src/replay.rs:173:30
    |
173 | ...                   e.to_string()
    |                        ^^^^^^^^^^^^ help: remove this
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_in_format_args

error: `to_string` applied to a type that implements `Display` in `error!` args
   --> system/core/init/libprefetch/prefetch/src/replay.rs:190:22
    |
190 |                     e.to_string()
    |                      ^^^^^^^^^^^^ help: remove this
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_in_format_args

error: `to_string` applied to a type that implements `Display` in `error!` args
   --> system/core/init/libprefetch/prefetch/src/tracer/mod.rs:118:20
    |
118 |                 ret.to_string()
    |                    ^^^^^^^^^^^^ help: remove this
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#to_string_in_format_args
```

Bug: 421269002
Test: m rust
Flag: EXEMPT refactor
Change-Id: I6bfeb0511ef50a663a5b64393aeaf9da2d2a5a71