Fix a bug returning 404 when display a single tag with no release (#29466)

Partially caused by #29149 

When use

```go
releases, err := getReleaseInfos(ctx, &repo_model.FindReleasesOptions{
		ListOptions: db.ListOptions{Page: 1, PageSize: 1},
		RepoID:      ctx.Repo.Repository.ID,
		TagNames:    []string{ctx.Params("*")},
		// only show draft releases for users who can write, read-only users shouldn't see draft releases.
		IncludeDrafts: writeAccess,
	})
```
replace
```go
release, err := repo_model.GetRelease(ctx, ctx.Repo.Repository.ID, ctx.Params("*"))
```
It missed `IncludeTags: true,`. That means this bug will be occupied only when the release is a tag.
This PR will fix

 - Get the right tag record when it's not a release
 - Display correct tag tab but not release tag when it's a tag.
- The button will bring the tag name to the new page when it's a single tag page
- the new page will automatically hide the release target inputbox when the tag name is pre filled. This should be backport to v1.21.

web_src/js/features/repo-release.js

@@ -30,8 +30,9 @@ function initTagNameEditor() {
   const newTagHelperText = el.getAttribute('data-tag-helper-new');
   const existingTagHelperText = el.getAttribute('data-tag-helper-existing');
 
-  document.getElementById('tag-name').addEventListener('keyup', (e) => {
-    const value = e.target.value;
+  const tagNameInput = document.getElementById('tag-name');
+  const hideTargetInput = function(tagNameInput) {
+    const value = tagNameInput.value;
     const tagHelper = document.getElementById('tag-helper');
     if (existingTags.includes(value)) {
       // If the tag already exists, hide the target branch selector.
@@ -41,6 +42,10 @@ function initTagNameEditor() {
       showElem('#tag-target-selector');
       tagHelper.textContent = value ? newTagHelperText : defaultTagHelperText;
     }
+  };
+  hideTargetInput(tagNameInput); // update on page load because the input may have a value
+  tagNameInput.addEventListener('input', (e) => {
+    hideTargetInput(e.target);
   });
 }