This commit is a part of the efforts to rename btn-related classes
and variables to align with Zulip's no-abbreviations policy and
streamline the search results.
This commit improves the copy codeblock button and playground button
in the codeblocks to improve their visibility, particularly when on
top of some code.
Previously, the text under these buttons was difficult to select, as the
buttons would block the selection. This commit now hides these buttons
when a user clicks on any part of the codeblock, allowing to view the
code without any distractions, as well as, allowing the user to select
any part of the code.