feat: add --add-default-collectors flag to preflight

[xavpaice]

For the preflight binary, add a --add-default-collectors flag, default true.

If set to false, do not add cluster-resources and cluster-info to the list of collectors in a preflight.

Fixes: #1447

Checklist

• New and existing tests pass locally with introduced changes.
• Tests for the changes have been added (for bug fixes / features)
• The commit message(s) are informative and highlight any breaking changes
• Any documentation required has been added/updated. For changes to https://troubleshoot.sh/ create a PR here

Does this PR introduce a breaking change?

• Yes
• No

[xavpaice]

Test:

spec:

apiVersion: troubleshoot.sh/v1beta2
kind: Preflight
metadata:
  name: connectivity
spec:
  collectors:
    - runPod:
        name: connectivity
        namespace: default
        podSpec:
          containers:
            - name: wget
              image: busybox:1
              command: ["wget"]
              args: ["-O", "-", "https://docs.replicated.com"]

  analyzers:
    - textAnalyze:
        checkName: "connectivity"
        fileName: connectivity/connectivity.log
        regex: 'title=\"Replicated Docs\"'
        outcomes:
          - pass:
              when: "true"
              message: Successful download from from https://docs.replicated.com
          - fail:
              message: Was unable to download from https://docs.replicated.com

Set flag false:

$ time ./bin/preflight --interactive=false --add-default-collectors=false ./preflight.yaml
name: run-pod              status: running         completed: 0    total: 1   
name: run-pod              status: completed       completed: 1    total: 1   

   --- PASS connectivity
      --- Successful download from from https://docs.replicated.com
--- PASS   connectivity
PASS
./bin/preflight --interactive=false --add-default-collectors=false   0.06s user 0.03s system 1% cpu 7.369 total

Default (true):

$ time ./bin/preflight --interactive=false ./preflight.yaml 
name: cluster-resources    status: running         completed: 0    total: 3   
name: cluster-resources    status: completed       completed: 1    total: 3   
name: run-pod              status: running         completed: 1    total: 3   
name: run-pod              status: completed       completed: 2    total: 3   
name: cluster-info         status: running         completed: 2    total: 3   
name: cluster-info         status: completed       completed: 3    total: 3   

   --- PASS connectivity
      --- Successful download from from https://docs.replicated.com
--- PASS   connectivity
PASS
./bin/preflight --interactive=false ../reliability-matrix/dev/preflight.yaml  0.37s user 0.10s system 0% cpu 1:06.46 total

[xavpaice]

Closing - there's an alternate which works better (use exclude)