add gocritic/ruleguard checks back again, cleanup code. (#13665)

- remove some duplicated code
- reported a bug, separately fixed in #13664
- using strings.ReplaceAll() when needed
- using filepath.ToSlash() use when needed
- remove all non-Go style comments from the codebase

Co-authored-by: Aditya Manthramurthy <donatello@users.noreply.github.com>

.golangci.yml

@@ -23,12 +23,19 @@ linters:
     - structcheck
     - unconvert
     - varcheck
+    - gocritic
 
 issues:
   exclude-use-default: false
   exclude:
       - should have a package comment
       - error strings should not be capitalized or end with punctuation or a newline
+      # todo fix these when we get enough time.
+      - "singleCaseSwitch: should rewrite switch statement to if statement"
+      - "unlambda: replace"
+      - "captLocal:"
+      - "ifElseChain:"
+      - "elseif:"
 
 service:
-  golangci-lint-version: 1.20.0 # use the fixed version to not introduce new linters unexpectedly
+  golangci-lint-version: 1.43.0 # use the fixed version to not introduce new linters unexpectedly