backport #22246
Since #20218 introduced internal watching template, template watching
should be removed from `air`. This will prevent restart the whole server
once the template files changed to speed up developing when using `make
watch`.
To ensure `make watch` will reuse template watching, this PR introduced
a new ENV `GITEA_RUN_MODE` to make sure `make watch` will always run in
a dev mode of Gitea so that template watching will open.
This PR also added more exclude testdata directories.
Co-authored-by: 6543 <6543@obermui.de>
Lunny Xiao
Gusted
silverwind