Rollup merge of #136404 - fmease:rm-compiletest-relic-of-the-past, r=Noratrieb,jieyouxu

Remove a footgun-y feature / relic of the past from the compiletest DSL

The compiletest DSL still features a historical remnant from the time when its directives were merely prefixed with `//` instead of `//`@`` when unknown directive names weren't rejected since they could just as well be part of prose:

As an "optimization", it stops looking for directives once it stumbles upon a line which starts with either `fn` or `mod`. This is super footgun-y as it obviously leads to any seeming compiletest directives below `fn` and `mod` items getting completely ignored.

See #136403 for a practical example. As well the assembly test updated in this PR.

~~Blocked on #136403.~~ (merged)

0 files changed, 0 insertions, 0 deletions