tests: fix CI warning and distcheck failures

[rgerhards]

Summary

• correct the test array-length macro so modern compilers do not reject it under -Werror
• keep executable test programs out of the source-distribution file list
• use rsyslog's named test-group convention for the distributed shell test drivers

Why

The first GitHub Actions run exposed a long-standing invalid sizeof calculation and a distcheck failure caused by distributing the chk_version executable target.

Validation

• autoreconf -fvi
• ./configure
• make check (17 tests)
• make distcheck

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Summary by cubic

Fixes CI compile warnings and distcheck failures by correcting the array-length macro and distributing only shell test drivers. Also aligns test naming with rsyslog’s test-group convention and keeps chk_version out of the source tarball.

• Bug Fixes
  • Corrected NELEM to use sizeof((x)[0]) so modern compilers don’t warn under -Werror.
  • Split TESTS into TESTS_DEFAULT and limited EXTRA_DIST to shell test drivers; exclude check programs like chk_version so they build in distcheck.
  • Adopted rsyslog-style named test-group convention for distributed shell test drivers.

^{Written for commit 1b6be54. Summary will update on new commits.}