[Tigron]: roadmap and tracking epic for work on test tooling

## PR

### Done

- [x] #4056
- [x] #4076
- [x] #4079
- [x] #4080
- [x] #4081
- [x] #4116
- [x] #4111

### Pending review

### Work in progress

- [ ] #4129

## Test suites to rewrite

- [ ] STARTED: builder
- [x] completion
- [ ] TODO: compose
- [ ] STARTED: container
- [x] image
- [x] ipfs
- [ ] STARTED: login
- [x] network
- [x] system
- [x] volume
- [x] main

## Issues and features

- [ ] P0: there is currently no protection against identically named tests - since we use identifiers based on test names, this could be a problem when inadvertently identical names
- [ ] P0: remove dependency on *testing.T and replace by tig.T everywhere
- [ ] P1: requirements should be able to manipulate the environment
- [ ] P2: separate environment processing into a distinct struct for better debugability
- [ ] P1: API breaking: change comparators signature (remove `info` + `tig.T`)
- [ ] P0: `Manager` is evaluated before the command runs, while the `Comparator` in Output is evaluated after - this is confusing and prevents legit scenarios. Manager should only be evaluated after the command has run.
- [x] P0: rethink `Data` - need something to manipulate temp files (#4081)
- [x] P1: separate cwd and temp dir
- [ ] P1: following the rewrite of Command, test.Command is now a (mostly) empty shell - cleanup / refactor
- [x] P1: reintroduce Env, WD, etc to the command debug output
- [x] P1: add Config/Data details to the debug output
- [x] P1: currently, the command is executing inside data.TempDir(), so, there is no distinction between `.` and `TempDir` from the command perspective. We may want to address that.
- [ ] P1: missing something like `.AddCleanup()` when a routine inside `Setup` does want to add additional cleaning
- [ ] P2: use of data.Identifier in subtests hoping to get the parent testid may be error prone - rethink Identifier()?