binary classifier: detect elixir release-candidate versions (#4851)

The elixir-binary and elixir-library classifiers' regexes only matched
the bare semver triplet (and a single sub-segment for the library), so
release-candidate elixir images were either missed entirely or had
their version truncated:

  $ syft -q elixir:1.12.0-rc | grep elixir   # nothing
  $ syft -q elixir:1.13.0-rc.0 | grep elixir
  elixir   1.13.0   binary                   # truncated, "-rc.0" lost

Extend the version capture group to optionally include
"-<a-z0-9>+(\\.<digits>)?" so "1.12.0-rc.1", "1.13.0-rc.0", etc. match
exactly as the elixir.app and the binary's ELIXIR_VERSION line have
them.

Add a logical fixture under testdata/classifiers/snippets/elixir/
1.12.0-rc.1/linux-amd64 (cloned from the existing 1.19.1 fixture with
just the version strings changed) and register it in
Test_Cataloger_PositiveCases.

Closes #4819

Signed-off-by: Chris (ChrisJr404) <11917633+ChrisJr404@users.noreply.github.com>
Co-authored-by: Chris (ChrisJr404) <11917633+ChrisJr404@users.noreply.github.com>

syft/pkg/cataloger/binary/classifier_cataloger_test.go

@@ -1754,6 +1754,25 @@ func Test_Cataloger_PositiveCases(t *testing.T) {
 				},
 			},
 		},
+		{
+			// release-candidate elixir image — pre-fix the matchers stripped the
+			// "-rc.1" suffix from the elixir-library result and missed the
+			// elixir-binary entirely (#4819).
+			logicalFixture: "elixir/1.12.0-rc.1/linux-amd64",
+			expected: pkg.Package{
+				Name:      "elixir",
+				Version:   "1.12.0-rc.1",
+				Type:      "binary",
+				PURL:      "pkg:generic/elixir@1.12.0-rc.1",
+				Locations: locations("elixir", "lib/elixir/ebin/elixir.app"),
+				Metadata: pkg.BinarySignature{
+					Matches: []pkg.ClassifierMatch{
+						match("elixir-binary", "elixir"),
+						match("elixir-library", "lib/elixir/ebin/elixir.app"),
+					},
+				},
+			},
+		},
 		{
 			logicalFixture: "istio_pilot-discovery/1.29.0-alpha.0/linux-amd64",
 			expected: pkg.Package{