Don't display empty rendered attrs in Task Instance Details page

[josh-fell]

Closes: #29515

The Task Instance Details page was displaying attributes which did not have a value. Mainly these were the docs attributes (i.e. doc, doc_json, doc_md, doc_rst, and doc_yaml). This clutters the page with less useful information for the task instance.

This PR changes the attributes displayed on the page only if they have non-emptyvalues generally.

Current Task Instance Details with no doc attribute provided

New Task Instance Details with no doc or other special rendered attributes

Current Task Instance Details with bash_command and only doc_md provided
There are other special-rendered like sql and hql but let's use a BashOperator as an example.

New Task Instance Details with bash_command and only doc_md provided

[pierrejeambrun]

I believe this would hide the attribute for all falsy values. (0, "", [], etc...). Maybe we only want to skip when the value is actually None ?

[josh-fell]

I believe this would hide the attribute for all falsy values. (0, "", [], etc...). Maybe we only want to skip when the value is actually None ?

Yes, which is actually doc, doc_json, doc_rst, and doc_yaml (empty strings I guess). doc_md does display None. But I could track down why those are all not None if you feel that we should only filter out None. WDYT?

[pierrejeambrun]

I think it's ok like this. Attribute are taken from get_attr_renderer and it seems that all of them are 'string'. Skipping falsy values looks good.

(I was concerned that some attributes could be of different types, like boolean or int for instance, but it doesn't seem like so)