Move some Actions related functions from routers to services (#33280)

Move the main logic of `generateTaskContext` and `findTaskNeeds` to the
`services` layer.

This is a part of #32751, since we need the git context and `needs` to
parse the concurrency expressions.

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

services/actions/context_test.go

@@ -0,0 +1,29 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package actions
+
+import (
+	"context"
+	"testing"
+
+	actions_model "code.gitea.io/gitea/models/actions"
+	"code.gitea.io/gitea/models/unittest"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFindTaskNeeds(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+
+	task := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionTask{ID: 51})
+	job := unittest.AssertExistsAndLoadBean(t, &actions_model.ActionRunJob{ID: task.JobID})
+
+	ret, err := FindTaskNeeds(context.Background(), job)
+	assert.NoError(t, err)
+	assert.Len(t, ret, 1)
+	assert.Contains(t, ret, "job1")
+	assert.Len(t, ret["job1"].Outputs, 2)
+	assert.Equal(t, "abc", ret["job1"].Outputs["output_a"])
+	assert.Equal(t, "bbb", ret["job1"].Outputs["output_b"])
+}