NUTCH-3211 Skip SonarCloud when test artifacts are absent; pin Ubuntu runners before ubuntu-latest moves to 26.04

[lewismc]

PR for NUTCH-3211. Another of these PR's where it can't be properly tested before it runs on master.

When master pull request ci path-filters tests, JUnit report, SonarCloud, and the tests job no longer treats missing artifacts / a failed JaCoCo run as a hard failure. Ubuntu jobs pin ubuntu-24.04 (artifact names are *-linux-jdk17) so when ubuntu-latest becomes 26.04 on 19 Oct 2026, we do not move CI unexpectedly.

[github-actions]

Apache Yetus test-patch report

+1 overall

Vote	Subsystem	Runtime	Log	Comment
				Prechecks
+1	dupname	0m 0s		No case conflicting files found.
+1	@author	0m 0s		The patch does not contain any @author tags.
				master Compile Tests
				Patch Compile Tests
+1	codespell	0m 2s		No new issues.
+1	detsecrets	0m 31s		No new issues.
+1	blanks	0m 0s		The patch has no blanks issues.
+1	yamllint	0m 2s		No new issues.
				Other Tests
+1	asflicense	0m 1s		The patch does not generate ASF License warnings.
		0m 40s

Subsystem	Report/Notes
GITHUB PR	#966
Optional Tests	dupname asflicense codespell detsecrets yamllint
uname	Linux 4a361a2223d0 6.17.0-1022-azure #22-Ubuntu SMP Mon Jul 27 17:24:03 UTC 2026 x86_64 x86_64 x86_64 GNU/Linux
Build tool	nobuild
Personality	/github/workspace/.yetus/personality.sh
git revision	master / d5c7028
modules	C: . U: .
versions	git=2.34.1 codespell=2.4.1 detsecrets=1.5.0 yamllint=1.35.1
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