Expand `$autoload` parameter documentation of `add_option()` and `update_option()`

[flixos90]

As outlined with more context in #42441 and #58962, "excessive autoloading" (i.e. autoloading too many options) can lead to performance problems, in some cases huge ones that even cause bugs.

Part of the problem is that there is very little documentation on option autoloading, which makes it challenging for the WordPress ecosystem to understand and properly use it. This also is reflected in extremely limiting, and possibly even misleading inline documentation of the $autoload parameter of add_option() and update_option().

This ticket aims to update said inline documentation to provide additional context on what the parameter does and how it should be used.

Improving inline doc for the add_option(), and update_option()

Trac ticket: https://core.trac.wordpress.org/ticket/58963

[rajinsharwar]

Let me know if anything is missed or overdone @flixos90. Thanks!

[flixos90]

Thank you for the pull request @rajinsharwar! I left some feedback.

[rajinsharwar]

Hi @flixos90, updated the PR following your suggestion. Requesting a re-review.

Thank you @Rajinsharwar for the updates! Note that there are a few coding standards violations flagged in GitHub, for example indentation of inline doc parameter descriptions needs to use spaces, not tabs. Would you mind fixing these violations?

[rajinsharwar]

Sure! Just fixed those coding standards issues, can you please take a look now? @flixos90

[rajinsharwar]

Updated the confusing line as well :) @flixos90

[flixos90]

In 56370:

Options, Meta APIs: Expand $autoload parameter documentation.

This changeset expands documentation of the $autoload parameter of the add_option() and update_option() functions, in order to provide more context on what autoloading is and which considerations should go into the decision whether to autoload an option.

Excessive autoloading of options can lead to severe performance problems on some sites, and lack of documentation is a partial cause for the issue.

Props rajinsharwar.
Fixes #58963.

Committed in https://core.trac.wordpress.org/changeset/56370