The istio pilot-agent/pilot-discovery classifiers missed every
-snapshot.N build and the older -alpha.N/-beta.N/-rc.N layouts.
Two defects:
1. The doubled-version matcher anchored on a bare x.y.z followed by
NULs, but pre-release builds repeat the full version including the
suffix (1.15.0-beta.0 NUL NUL NUL 1.15.0-beta.0), so the anchor never
matched. Only the capture group had been widened previously.
2. -snapshot.N was absent from every alternation, and snapshot builds
store the version only once with no leading copy, so no existing
matcher could reach it.
Widen the leading anchor to accept the same optional pre-release suffix
it already accepts in the capture group, add -snapshot.N to each
alternation, and add a matcher for the standalone snapshot layout. The
new matcher is second so it can never shadow a normal build.
Adds real captured snippets for pilot-agent and pilot-discovery at
1.0.0-snapshot.0, 1.5.0-alpha.0, 1.15.0-beta.0 and 1.19.0-rc.0.
Fixes#5060
Signed-off-by: phatlc <phatle.hsd@gmail.com>
