Add context when rendering labels or emojis (#23281)

This branch continues the work of #23092 and attempts to rid the
codebase of any `nil` contexts when using a `RenderContext`.

Anything that renders markdown or does post processing may call
`markup.sha1CurrentPatternProcessor()`, and this runs
`git.OpenRepository()`, which needs a context. It will panic if the
context is `nil`. This branch attempts to _always_ include a context
when creating a `RenderContext` to prevent future crashes.

Co-authored-by: Kyle D <kdumontnu@gmail.com>

templates/projects/view.tmpl

@@ -234,7 +234,7 @@
 						{{if or .Labels .Assignees}}
 						<div class="extra content labels-list gt-p-0 gt-pt-2">
 							{{range .Labels}}
-								<a target="_blank" href="{{$.RepoLink}}/issues?labels={{.ID}}">{{RenderLabel .}}</a>
+								<a target="_blank" href="{{$.RepoLink}}/issues?labels={{.ID}}">{{RenderLabel $.Context .}}</a>
 							{{end}}
 							<div class="right floated">
 								{{range .Assignees}}