Remove new-from-rev from the linter (#1783)

* Fix all revive warnings in the code base

All of these are of the form

```
var Identifier Type = Expr
```

where the `Type` is known from the output of `Expr` and can be omitted
as a result.

* Handle unchecked errors

* Remove new-from-rev

Since the project passes all linter checks now, including older
revisions, we can remove new-from-rev. While here, reorder the linter
config file, and move the enabled linters up and settings down.

* Fix failing test cases

Studio & Performer export tests use local time rather than UTC. This
fixes the test cases so integration test
passes.

.golangci.yml

@@ -3,10 +3,23 @@ run:
   timeout: 3m
   modules-download-mode: vendor
 
-issues:
-  # Rev at which the linter was introduced. Older bugs are still
-  # present, but should not be considered validation errors for now
-  new-from-rev: b14d5c56504dfcea2f5a7b86706b0ecdafd0b68c
+linters:
+  disable-all: true
+  enable:
+    # Default set of linters from golangci-lint
+    - deadcode
+    - errcheck
+    - gosimple
+    - govet
+    - ineffassign
+    - staticcheck
+    - structcheck
+    - typecheck
+    - unused
+    - varcheck
+    # Linters added by the stash project
+    - gofmt
+    - revive
 
 linters-settings:
   gofmt:
@@ -52,21 +65,3 @@ linters-settings:
       - name: unreachable-code
       - name: redefines-builtin-id
 
-linters:
-  disable-all: true
-  enable:
-    # Default set of linters from golangci-lint
-    - deadcode
-    - errcheck
-    - gosimple
-    - govet
-    - ineffassign
-    - staticcheck
-    - structcheck
-    - typecheck
-    - unused
-    - varcheck
-    # Linters added by the stash project
-    - gofmt
-    - revive
-