feat(dotfiles): add sort and filter options to alias/var list (#3131)

groundwork for #2155. These functions can be reused when building the
interactive TUI.

Adds `--sort-by`, `--reverse`, `--name`, and `--value` flags to `atuin
dotfiles alias list` and `atuin dotfiles var list`. Also adds
`--exports-only` and `--shell-only` for vars.

happy to expand (or reduce?) on this if needed.


<details>
<summary>**Demo/Examples:**</summary>

`$atuin dotfiles alias list --reverse`
```bash
vim=nvim
py=python3
ll=ls -la
k=kubectl
gs=git status
gp=git push
gd=git diff
gc=git commit
dc=docker-compose
d=docker
```

`$atuin dotfiles alias list --sort-by value`
```bash
d=docker
dc=docker-compose
gc=git commit
gd=git diff
gp=git push
gs=git status
k=kubectl
ll=ls -la
vim=nvim
py=python3
```

`$atuin dotfiles alias list -n g`
```bash
gc=git commit
gd=git diff
gp=git push
gs=git status
```

`$atuin dotfiles var list --exports-only`
```bash
export EDITOR=vim
export LANG=en_US.UTF-8
export PAGER=less
export RUST_BACKTRACE=1
```

</details>

## Checks
- [x] I am happy for maintainers to push small adjustments to this PR,
to speed up the review cycle
- [x] I have checked that there are no existing pull requests for the
same thing

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