Replace heapless with the much smaller arrayvec

[parasyte]

heapless has surprisingly a lot of dependencies, and the only thing it is used for is a stack-allocated string in the panic handler. None of these dependencies are needed.

├── crankstart v0.1.2
│   ├── anyhow v1.0.75
│   ├── crankstart-sys v0.1.2
│   ├── cstr_core v0.1.2
│   │   ├── cty v0.1.5
│   │   └── memchr v2.6.3
│   ├── euclid v0.22.9 (*)
│   ├── hashbrown v0.14.0 (*)
│   └── heapless v0.6.1
│       ├── as-slice v0.1.5
│       │   ├── generic-array v0.12.4
│       │   │   └── typenum v1.16.0
│       │   ├── generic-array v0.13.3
│       │   │   └── typenum v1.16.0
│       │   ├── generic-array v0.14.7
│       │   │   └── typenum v1.16.0
│       │   └── stable_deref_trait v1.2.0
│       ├── generic-array v0.14.7 (*)
│       ├── hash32 v0.1.1
│       │   └── byteorder v1.4.3
│       └── stable_deref_trait v1.2.0

After replacing it with arrayvec:

├── crankstart v0.1.2
│   ├── anyhow v1.0.75
│   ├── arrayvec v0.7.4
│   ├── crankstart-sys v0.1.2
│   ├── cstr_core v0.1.2
│   │   ├── cty v0.1.5
│   │   └── memchr v2.6.3
│   ├── euclid v0.22.9 (*)
│   └── hashbrown v0.14.0 (*)

Much better!

[boozook]

Good point!
I'll just test it and merge soon.
Thank you!