Add manifest file to each each reference test

[Sandijigs]

Description

 This PR adds a `manifest.yaml` file to every generated test vector. The manifest contains
 the test's metadata (config, fork, runner, handler, suite, and case names) which was
 previously only available by parsing the directory path.
 This makes it easier to distribute individual test vectors without losing context about
 what they're testing. It also helps when refactoring the directory structure since the
 metadata is now embedded in each test case.

Changes Made

 - Added `dump_manifest()` method in `dumper.py` to generate the manifest file
 - Updated `gen_runner.py` to call `dump_manifest()` after writing test outputs
 - Documented the manifest format in `tests/formats/README.md`

• Update documentation
• Add tests for new functionality
• Run make lint to check formatting
• Run make test to check tests

Fixes #4602

[Sandijigs]

Hi @leolara , Please help review the changes made to this issue

[leolara]

@Sandijigs check the produced manifest.yaml

{config_name: minimal, fork_name: phase0, runner_name: epoch_processing, handler_name: eth1_data_reset,
suite_name: pyspec_tests, case_name: eth1_vote_no_reset}

It should not look like that, but like the data.yaml for example

[Sandijigs]

Okay @leolara

[leolara]

@Sandijigs are you doing it?

[Sandijigs]

yes , @leolara . I am currently on it ,

[leolara]

LGTM 🚀

I would perhaps change the README, to indicate that the directory structure is the legacy style of figuring out this data.

[jtraglia]

Made some little improvements. LGTM. @leolara feel free to merge/modify as you see fit.