feat: warn when it looks like you're using ignore instead of exclude directive (#1955)
**What type of PR is this?**
Feature
**What package or component does this PR mostly affect?**
all
**What does this PR do? Why is it needed?**
`ignore` and `exclude` are somewhat confusing directive names, and are
easily mixed up. Show a warning when using the `gazelle:ignore`
directive with an argument.
I've seen many places where people do something like `# gazelle:ignore
testdata` and accidentally disable gazelle for the entire directory and
subdirectories. This can be seen in [many public github
repos](https://github.com/search?q=%2F%23+gazelle%3Aignore+.%2F+language%3AStarlark&type=code&l=Starlark).
**Other notes for review**
Add a new generated test directory to assert that the warning is shown
correctly.
10 files changed
