This reverts commit c1826eb.

Implement Default for CompactFormatter

Add Clone and Debug impls to map iterators

Older versions produce slightly differently normalized output
when run against 1.90.0+ Rust compiler.

Raise required compiler to Rust 1.61

Switch serde dependency to serde_core

    warning: variables can be used directly in the `format!` string
       --> src/ser.rs:448:15
        |
    448 |         match write!(adapter, "{}", value) {
        |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
        = note: `-W clippy::uninlined-format-args` implied by `-W clippy::pedantic`
        = help: to override `-W clippy::pedantic` add `#[allow(clippy::uninlined_format_args)]`
    help: change this to
        |
    448 -         match write!(adapter, "{}", value) {
    448 +         match write!(adapter, "{value}") {
        |

    warning: variables can be used directly in the `format!` string
       --> src/value/mod.rs:182:37
        |
    182 |             Value::Bool(boolean) => write!(formatter, "Bool({})", boolean),
        |                                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
    help: change this to
        |
    182 -             Value::Bool(boolean) => write!(formatter, "Bool({})", boolean),
    182 +             Value::Bool(boolean) => write!(formatter, "Bool({boolean})"),
        |

    warning: variables can be used directly in the `format!` string
       --> src/value/mod.rs:184:38
        |
    184 |             Value::String(string) => write!(formatter, "String({:?})", string),
        |                                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
    help: change this to
        |
    184 -             Value::String(string) => write!(formatter, "String({:?})", string),
    184 +             Value::String(string) => write!(formatter, "String({string:?})"),
        |

    warning: variables can be used directly in the `format!` string
       --> src/number.rs:365:9
        |
    365 |         write!(formatter, "Number({})", self)
        |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#uninlined_format_args
    help: change this to
        |
    365 -         write!(formatter, "Number({})", self)
    365 +         write!(formatter, "Number({self})")
        |