Follow-up to https://github.com/go-gitea/gitea/pull/37571.
"Participating and mentions" deleted the watch row, so choosing it
dropped you out of the watcher count. It is a watch like the others, so
it now keeps a row and simply subscribes to no events.
The dashboard feed ignored the per-event options, so a "Custom: issues"
watcher still got pull request activity there. It now gates on the same
options as mail and notifications. That also closes a gap where pull
request reviews bypassed the permission check.
Also, address
https://github.com/go-gitea/gitea/pull/37571#discussion_r3740487363 and
reword a UI text for clarity.
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Signed-off-by: silverwind <me@silverwind.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
silverwind