add support for --list-software --output-format=json

[APN-Pucky]

This could be a first step on getting easybuild on repology as described here:

• adding EasyBuild repology/repology-updater#705

Next steps would be:

• handle name collisions
• serving the json to repology on some server/page (since they don't want to run third party software).

Possibly related:

• added option to EB to dump information about EasyConfig files #1644

Please let me know, if the (estimated) effort to get easybuild on repology is worth it.
The json format might be useful either way.

Cheers,
APN

• eb --avail-cfgfile-constants --output-format json
• eb --avail-easyconfig-constants --output-format json
• eb --avail-easyconfig-licenses --output-format json
• eb --avail-easyconfig-params --output-format json
• eb --avail-easyconfig-templates --output-format json
• eb --avail-toolchain-opts ... --output-format json
• eb --list-easyblocks --output-format json
• eb --list-software --output-format json
• eb --list-toolchains --output-format json
  - [ ] eb --help json
• gen_easyblocks_overview_json

[boegel]

@APN-Pucky It would definitely be interesting to get EasyBuild into repology!

High-level, the changes being made here look like a good start, but:

• tests should be enhanced as well to make sure that --list-software --output-format=json works (and keeps working) as intended;
• add json as a supported output format makes sense, but implies that all other options that also take into account the selected output format should be updated to support producing JSON. add support for using --output-format=md (MarkDown) #4117 shows that this is no small effort, but maybe it makes sense to somehow only support --output-format=json for --list-software, without causing trouble for the other options;
• merge conflicts will appear once add support for using --output-format=md (MarkDown) #4117 gets merged (although they'll likely be easy to resolve);

[APN-Pucky]

1. resolved conflict with md format
2. added the other json format functions with NotImplementedError exceptions. They are also checked in the test, so that when I or someone else extends the json format one gets reminded of the tests.
3. added --list-software --output-format=json tests

[APN-Pucky]

Seems to be only some newlines. While it worked for me I'll just replace the failed newlines with those that worked in the CI.

[APN-Pucky]

So finally, after sorting and tuning the json for compatibility across different python versions, my CI runs through too... (https://github.com/APN-Pucky/easybuild-framework/actions/runs/7114626894)

[boegel]

lgtm