feat: add index management commands

[Jonas-Puksta-Sensmetry]

• Resolves Add index management command #279
• Resolves Design and implement yanking functionality under index management command #301

[Jonas-Puksta-Sensmetry]

@andrius-puksta-sensmetry @consideRatio I'll add more tests and update documentation, but other parts are ready for review

[consideRatio]

Nice @Jonas-Puksta-Sensmetry!!

I let codex make two PRs reflecting the two main non-blocking feedback points I had:

1. I see index_utils.rs to contain shared data models between env/index.rs and commands/index/..., but think _utils doesn't reflect that, so I refactored it into index/{model|iri}.rs instead
   PR to your PR with this change: Jonas-Puksta-Sensmetry#1
2. I see commands/index/mod_tests.rs as integration tests, and as such they would belong into the core/tests folder.
   PR to your PR with this change, and point 1, Jonas-Puksta-Sensmetry#2

[consideRatio]

Jonas highlighted these as action points:

• The following isn't yet done. When adding a project version, if some copying/writing fails, try to remove the directory of that specific version
• Also I haven't updated the documentation

@andrius-puksta-sensmetry could you consider merge of these? Then I figure we act on Jonas points ourselves.

My input in #335 (review):

1. I see index_utils.rs to contain shared data models between env/index.rs and commands/index/..., but think _utils doesn't reflect that, so I refactored it into index/{model|iri}.rs instead
   PR to your PR with this change: Move shared index types out of index_utils Jonas-Puksta-Sensmetry/sysand#1
2. I see commands/index/mod_tests.rs as integration tests, and as such they would belong into the core/tests folder.
   PR to your PR with this change, and point 1, Make index command tests to integration tests Jonas-Puksta-Sensmetry/sysand#2

[andrius-puksta-sensmetry]

Suggested change

	you can add it to the package index by (provided .project.json specifies
	`publisher` field):
	you can add it to the package index by (provided `.project.json` specifies
	matching `publisher` and `name` fields):

Ideally there would be at least two examples:

1. Project with appropriate (i.e. normalizable) publisher and name and no --iri given.
2. Project without publisher and with --iri given
3. (maybe) project with non-normalizable publisher/name and with --iri given
4. (maybe) project without a publisher and with --iri given

Alternatively/additionally, we should provide nice actionable error messages when publisher/name are not normalizable or publisher is missing, and direct people to give --iri when needed. Users will for sure find this whole situation of "optional publisher, and if publisher and name both satisfy specific rules, no --iri needs to be given; but if --iri PURL is given it must match publisher/name" confusing.

[andrius-puksta-sensmetry]

Some of this should go to a new doc page explaining Sysand PURL and how exactly it corresponds to projects.

[andrius-puksta-sensmetry]

None of this is urgent, but will have to be done soon-ish.

[andrius-puksta-sensmetry]

Good enough, we'll definitely need to improve errors and docs, but that can wait a bit.