Upgrade rust toolchain to 1.75.0

[eval-exec]

• Upgrade rust-toolchain to 1.75.0
• Apply cargo-clippy's suggestions

    Checking ckb-rocksdb v0.21.1 (/home/exec/Projects/github.com/nervosnetwork/rust-rocksdb)
error: accessing first element with `info.get(0)`
   --> src/backup.rs:394:29
    |
394 |             let backup_id = info.get(0).unwrap().backup_id;
    |                             ^^^^^^^^^^^ help: try: `info.first()`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#get_first
    = note: `-D clippy::get-first` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::get_first)]`

error: casting raw pointers to the same type and constness is unnecessary (`*const u8` -> `*const u8`)
   --> src/merge_operator.rs:209:21
    |
209 |                     *(ptr as *const *const u8) as *const u8,
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `*(ptr as *const *const u8)`
    |
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
    = note: `-D clippy::unnecessary-cast` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::unnecessary_cast)]`

error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
   --> src/ops/multi_get.rs:286:22
    |
286 |                 .zip(errors.into_iter())
    |                      ^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `errors`
    |
note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
   --> /home/exec/.rustup/toolchains/1.75.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:643:12
    |
643 |         U: IntoIterator,
    |            ^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion
    = note: `-D clippy::useless-conversion` implied by `-D warnings`
    = help: to override `-D warnings` add `#[allow(clippy::useless_conversion)]`

error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
   --> src/ops/multi_get.rs:310:14
    |
310 |         .zip(values_sizes.into_iter())
    |              ^^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `values_sizes`
    |
note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
   --> /home/exec/.rustup/toolchains/1.75.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:643:12
    |
643 |         U: IntoIterator,
    |            ^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion

error: explicit call to `.into_iter()` in function argument accepting `IntoIterator`
   --> src/ops/multi_get.rs:311:14
    |
311 |         .zip(errors.into_iter())
    |              ^^^^^^^^^^^^^^^^^^ help: consider removing the `.into_iter()`: `errors`
    |
note: this parameter accepts any `IntoIterator`, so you don't need to call `.into_iter()`
   --> /home/exec/.rustup/toolchains/1.75.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/iter/traits/iterator.rs:643:12
    |
643 |         U: IntoIterator,
    |            ^^^^^^^^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_conversion

error: could not compile `ckb-rocksdb` (lib test) due to 5 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `ckb-rocksdb` (lib) due to 4 previous errors
make: *** [Makefile:3: clippy] Error 101

[doitian]

There are some errors: db does not live long enough