chore(workflows/nightly.yml): create issue only on all platforms fail

[mweberxyz]

This relates to...

• Nightly tests are failing #3017 (comment)

Rationale

In the four nightly failures so far, 3 were not undici's fault and only one platform failed. In the one true positive error, all three platforms failed tests, therefore only create/comment issue if all three platform fail.

Sample Runs

1. All platforms succeed: https://github.com/mweberxyz/nodejs-undici/actions/runs/8491820300
   No issue created
2. Single platform fails: https://github.com/mweberxyz/nodejs-undici/actions/runs/8491975740
   No issue created
3. All platforms fail: https://github.com/mweberxyz/nodejs-undici/actions/runs/8491957840
   Issue created: Nightly tests are failing mweberxyz/nodejs-undici#8

Changes

.github/workflows/nightly.yml:

• remove matrix to give each platform a stable id
• only run report-failureif all three platforms fail

Features

N/A

Bug Fixes

N/A

Breaking Changes and Deprecations

N/A

Status

• I have read and agreed to the Developer's Certificate of Origin
• Tested
• Review ready
• In review
• Merge ready

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.51%. Comparing base (9278de9) to head (396a1a6).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3020   +/-   ##
=======================================
  Coverage   93.51%   93.51%           
=======================================
  Files          89       89           
  Lines       24231    24231           
=======================================
  Hits        22659    22659           
  Misses       1572     1572           

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[mcollina]

lgtm