Removes `testenv` annotations and related code. These annotations originally let you skip x-pack snippet tests in the docs. However, that's no longer possible.
Relates to #79309, #31619
In AsciiDoc, `subs="attributes,callouts,macros"` options were required
to render `include-tagged::` in a code block.
With elastic/docs#827, Elasticsearch Reference documentation migrated
from AsciiDoc to Asciidoctor.
In Asciidoctor, the `subs="attributes,callouts,macros"` options are no
longer needed to render `include-tagged::` in a code block. This commit
removes those unneeded options.
Resolves#41589
To avoid having to specify each spec by hand (which can miss specs to be
added), the test infrastructure now performs classpath discovery so that
each spec added, is automatically considered.
Relates #40358
