Fix bulk intermittent e2e tests

[Steve-Mcl]

Description

Fix intermittent e2e test fails on bulk ops.

Based on the captured logs, it seems to be always after selecting ff-check items. As though the "click" of an ff-check is somewhat async. Example:

Changes:

• Add some preliminary array length checks to aid with debugging when the test fails
• Add short 30ms delay AFTER checking checkboxes (handle async element)
• Add additional interlocks (like dialog shown, delete button enabled) etc that should cause cy to wait for elements

I did manage to get the e2e test to fail locally (took about 10 runs) but after these changes it appears to be stable 🤞

Related Issue(s)

No issue, just random, intermittent test fails.

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• Includes a DB migration? -> add the area:migration label

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.19%. Comparing base (c547148) to head (70d2c8d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4309   +/-   ##
=======================================
  Coverage   78.19%   78.19%           
=======================================
  Files         292      292           
  Lines       13440    13440           
  Branches     3007     3007           
=======================================
  Hits        10510    10510           
  Misses       2930     2930           

Flag	Coverage Δ
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