fix: generate macros for all subpackages

[PawelWMS]

Related to #15578.

Summary

Fixes a bug in versionsprocessor where the generated macros.releaseversions file only contained macros for the default (top-level) package of each spec, missing all subpackages with their own version, release, or epoch. Also fixes a related bug where every macro for a given spec was keyed off the spec file name, so subpackages with names different from the spec name effectively never received their own macros (each subpackage would just overwrite the default package's %azl_<spec>_* macros).

Bug 1: only the default package was queried

In processSpecFile() (toolkit/tools/versionsprocessor/versionsprocessor.go), the spec query was issued with rpm.QueryHeaderArgument (--srpm):

packages, err := rpm.QuerySPEC(specFile, sourceDir, `%{NAME}: %{evr}\n`, buildArch, defines, rpm.QueryHeaderArgument)

The --srpm flag instructs rpmspec to return only the source package header. Even though the surrounding code loops over packages expecting one entry per built RPM, the query only ever returns a single line for the SRPM's own NEVR. As a result, no %azl_<subpackage>_* macros were emitted for any subpackage declared via %package — only the default package got macros.

This was raised during the original review of #15578 (review comment) but the switch to --builtrpms was not applied, only the query format and regex changes.

Bug 2: subpackage macros used the spec file name

processPackageVersionString derived the macro name from the spec file's base name (e.g. kernel.spec → %azl_kernel_*) and then iterated over every queried package. Even after fixing Bug 1, every subpackage of a given spec would still write to the same %azl_<spec>_* macros, repeatedly overwriting the default package's values. Subpackages whose names differ from the spec name (e.g. kernel-headers, ca-certificates-shared, mlnx-ofa_kernel-devel) never produced their own dedicated macros.

Fix

• Switch from rpm.QuerySPEC(... QueryHeaderArgument) to rpm.QuerySPECForBuiltRPMs. This makes rpmspec return one line per binary RPM that would be built from the spec, including all subpackages with their individual epoch/version/release.
• Derive each macro name from the actual package name parsed out of the %{nevra} output, instead of from the spec file's base name. Each subpackage now gets its own %azl_<subpackage>_* set of macros.
• Reuse the existing rpmSpecBuiltRPMRegex / RpmSpecBuiltRPMRegex from rpmssnapshot by promoting it into internal/rpm (along with its index constants), and extend it to capture the optional epoch and to split version and release into separate groups.
• rpmssnapshot now consumes the shared regex and keeps its existing RepoPackage.Version shape (epoch:version-release) by recombining the split groups.
• processPackageVersionString no longer needs the spec file name or the dist tag: the package name comes from the regex, and the release no longer carries the dist tag (dist is its own capture group now), so the manual strings.Replace(release, distTag, "", 1) is gone.
• Lifted the per-package error context out of processPackageVersionString and into the caller (processSpecFile), where the spec file name is still in scope.
• Existing call sites passing --srpm for arch checks etc. are untouched.

After the fix, e.g. ca-certificates.spec yields macros for ca-certificates, ca-certificates-shared, ca-certificates-base, ca-certificates-tools, and ca-certificates-legacy — each with their own %azl_<subpackage>_version / _release (and _epoch when non-zero) — instead of just the default package.

Tests

• Moved the regex-only tests for RpmSpecBuiltRPMRegex from rpmssnapshot_test.go into rpm_test.go, where the regex now lives.
• Updated versionsprocessor_test.go for the new processPackageVersionString signature (NEVRA input, no specFileName/distTag arguments). Added a noarch case and an explicit subpackage-name assertion in TestProcessSpecFile_WithSubpackages, which now verifies distinct %azl_multipkg_*, %azl_multipkg_devel_*, and %azl_multipkg_libs_* macros.
• Updated rpmssnapshot_test.go for the expanded regex (epoch group added, version/release split) and added an epoch-bearing input to TestGenerateResults.
• All affected packages (internal/rpm, pkg/rpmssnapshot, versionsprocessor) pass with go test. The full toolkit/tools test run is otherwise green; the only failure is internal/pkggraph/TestReferenceDOTFile, which fails identically on origin/3.0-dev and is unrelated to this PR.