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>

modules/csv/csv_test.go

@@ -11,6 +11,7 @@ import (
 	"strings"
 	"testing"
 
+	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/markup"
 
 	"github.com/stretchr/testify/assert"
@@ -229,7 +230,10 @@ John Doe	john@doe.com	This,note,had,a,lot,of,commas,to,test,delimiters`,
 	}
 
 	for n, c := range cases {
-		delimiter := determineDelimiter(&markup.RenderContext{RelativePath: c.filename}, []byte(decodeSlashes(t, c.csv)))
+		delimiter := determineDelimiter(&markup.RenderContext{
+			Ctx:          git.DefaultContext,
+			RelativePath: c.filename,
+		}, []byte(decodeSlashes(t, c.csv)))
 		assert.EqualValues(t, c.expectedDelimiter, delimiter, "case %d: delimiter should be equal, expected '%c' got '%c'", n, c.expectedDelimiter, delimiter)
 	}
 }