chore: enable and fix some gocritic issues

[mmorel-35]

- What I did

enable and fix some gocritic issues

- How I did it

- How to test it

- Description for the changelog

[codecov-commenter]

Codecov Report

❌ Patch coverage is 22.50000% with 31 lines in your changes missing coverage. Please review.
✅ Project coverage is 14.73%. Comparing base (6e9e7b8) to head (939f5a4).
⚠️ Report is 68 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3287   +/-   ##
=======================================
  Coverage   14.73%   14.73%           
=======================================
  Files         200      200           
  Lines       93077    93028   -49     
=======================================
  Hits        13712    13712           
+ Misses      78019    77978   -41     
+ Partials     1346     1338    -8     

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[Copilot]

Pull request overview

This PR enables the gocritic linter in the repository’s golangci-lint configuration and applies a set of small refactors across the codebase to address the newly enabled gocritic findings, primarily simplifying conditional chains and avoiding unnecessary string operations.

Changes:

• Enable gocritic in .golangci.yml and configure it with enable-all: true plus a curated list of disabled checks.
• Refactor several if/else chains into conditionless switch statements to satisfy linter expectations and reduce nesting.
• Replace a small strings.Join usage with direct string concatenation and use strings.EqualFold for case-insensitive comparisons.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
swarmd/dockerexec/container.go	Simplifies label key construction by replacing strings.Join with string concatenation.
protobuf/plugin/deepcopy/deepcopy.go	Replaces if/else chains with switch blocks in generated-code emission logic.
manager/orchestrator/update/updater.go	Refactors task selection logic from if/else into a switch chain.
manager/orchestrator/restart/restart.go	Refactors service-type branching logic into a switch with grouped cases.
manager/orchestrator/jobs/replicated/reconciler.go	Reduces nesting by converting an inner conditional into an else if.
manager/logbroker/broker.go	Simplifies session subscription ID validation by removing an unnecessary else block.
manager/controlapi/cluster.go	Uses strings.EqualFold for clearer case-insensitive algorithm validation.
cli/external_ca.go	Uses strings.EqualFold for protocol parsing without allocating a lowercased copy.
ca/renewer.go	Refactors renewal retry decision logic into a switch chain.
ca/keyreadwriter.go	Minor comment formatting tweak in a switch case.
api/defaults/service.go	Removes superfluous nesting by converting nested if blocks into else if checks.
.golangci.yml	Enables and configures gocritic checks under the v2 config format.

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