grep: -q match yields exit 0 even after a file error

[sylvestre]

GNU grep documents that with -q the exit status is 0 as soon as a line is selected, even if an error (such as a missing file) occurred. uu_grep let had_error take precedence, so 'grep -q PAT missing -' returned 2 instead of 0 when stdin matched. Give quiet+match priority in finish(); without -q, or with -q and no match, a file error still yields exit 2. Fixes the GNU testsuite 'status' test.

[github-actions]

GNU grep testsuite comparison:

Test results comparison:
  Current:   TOTAL: 128 / PASSED: 71 / FAILED: 36 / SKIPPED: 21
  Reference: TOTAL: 128 / PASSED: 70 / FAILED: 37 / SKIPPED: 21

Changes from main branch:
  TOTAL: +0
  PASSED: +1
  FAILED: -1

Test improvements (1):
  + status

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.90%. Comparing base (98e6bb6) to head (399d2d1).

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #11      +/-   ##
==========================================
+ Coverage   95.82%   95.90%   +0.07%     
==========================================
  Files           6        6              
  Lines        1414     1416       +2     
  Branches      140      141       +1     
==========================================
+ Hits         1355     1358       +3     
+ Misses         58       57       -1     
  Partials        1        1              

Flag	Coverage Δ
macOS_latest	96.72% <100.00%> (+0.07%)	⬆️
ubuntu_latest	96.72% <100.00%> (+0.07%)	⬆️
windows_latest	0.00% <0.00%> (ø)

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