[meta] Reducing the number of dependencies

Medusa (Bernini)

Hello,

This project has too many dependencies according to me.

The number of dependencies (regardless of their versions, features etc.)

```shell
$ cargo tree --all-features --edges all --prefix none | rg -v '^$' | cut -d' ' -f 1 | sort | uniq | wc -l
539
```

This is a meta issue aiming at reducing the number of dependencies, thus reducing the compile-time, and the resulting binary size.

## Removing duplicated dependencies

We have 35 duplicated dependencies:

```shell
$ cargo tree --all-features --duplicates | rg '^[a-z]' | datamash -W groupby 1 collapse 2 | tr '\t,' ' ' | sed -E -e 's/^([a-z0-9_\-]+)/* [ ] `\1`:/' | sed -E -e 's/(v.*) v/\1, v/g' | sed -E -e 's/v([0-9]+)/\1/g'
```

* [ ] `bitflags`: 2.10.0, 2.10.0
* [ ] `camino`: 1.2.1, 1.2.1
* [ ] `crypto-common`: 0.1.6, 0.1.6
* [ ] `darling`: 0.20.10, 0.21.1
* [ ] `darling_core`: 0.20.10, 0.21.1
* [ ] `darling_macro`: 0.20.10, 0.21.1
* [ ] `derive_more`: 1.0.0, 2.0.1
* [ ] `derive_more-impl`: 1.0.0, 2.0.1
* [ ] `digest`: 0.10.7, 0.10.7
* [ ] `getrandom`: 0.2.15, 0.3.1
* [ ] `hashbrown`: 0.14.5, 0.15.2, 0.16.1
* [ ] `indexmap`: 2.12.1, 2.12.1
* [ ] `itertools`: 0.10.5, 0.13.0, 0.14.0
* [ ] `js_int`: 0.2.2, 0.2.2
* [ ] `libc`: 0.2.175, 0.2.175
* [ ] `phf`: 0.11.2, 0.13.1
* [ ] `phf_shared`: 0.11.2, 0.13.1
* [ ] `rand`: 0.8.5, 0.8.5
* [ ] `rand_core`: 0.6.4, 0.6.4, 0.9.3
* [ ] `ruma-identifiers-validation`: 0.12.0, 0.12.0
* [ ] `rustix`: 0.38.41, 1.0.8
* [ ] `semver`: 1.0.27, 1.0.27
* [ ] `serde`: 1.0.228, 1.0.228
* [ ] `serde_core`: 1.0.228, 1.0.228
* [ ] `sha2`: 0.10.9, 0.10.9
* [ ] `siphasher`: 0.3.11, 1.0.1
* [ ] `strum`: 0.26.3, 0.27.2
* [ ] `strum_macros`: 0.26.4, 0.27.1
* [ ] `syn`: 1.0.109, 2.0.101
* [ ] `thiserror`: 1.0.63, 2.0.17
* [ ] `thiserror-impl`: 1.0.63, 2.0.17
* [ ] `toml_datetime`: 0.6.8, 0.7.2
* [ ] `unicode-width`: 0.1.13, 0.2.0
* [ ] `webpki-roots`: 0.26.3, 1.0.2
* [ ] `winnow`: 0.6.20, 0.7.13

## Reviewing dependencies

A list of things we should do:

- reviewing the features, see if `default-features = false` can be used to avoid pulling useless dependencies,
- find dependencies that do similar things, and pick a single one of them,
- find dependencies where a smaller one might exist,
- any other ideas?