RFR: 8244624: Improve handling of JarFile META-INF resources

[Claes Redestad]

Hi,

currently during ZipFile creation, we create an int[] array of pointers
to META-INF entries. These are then retrieved from three different
places in JarFile.

However, JarFile is only interested in some combination a few things:
the existence of and name of the META-INF/MANIFEST file, the existence
of and the names of various signature related files, i.e., files in
META-INF that have a suffix such as .EC, .SF, .RSA and .DSA

Refactoring the contract between JarFile and ZipFile means we can filter
out such entries that we're not interested when opening the file, and
also remove the need to create the String for each entries unless we
actually want them:

Bug:    https://bugs.openjdk.java.net/browse/JDK-8244624
Webrev: http://cr.openjdk.java.net/~redestad/8244624/open.00/

This reduces retained footprint of Jar-/ZipFile by slimming down or
removing the Source.metanames array entirely, and a significant speed-up
in some cases.

In the provided microbenchmark, getManifestFromJarWithManifest and
getManifestFromJarWithSignatureFiles doesn't call
JUZFA.getMetaInfEntryNames but still see small (~5%) speed-up decrease
in allocations.

getManifestFromJarWithNoManifest exercise JUZFA.getMetaInfEntryNames in
the baseline, and now calls JUZFA.getManifestName. Result is a 1.25x
speed-up and 30% reduction in allocations. While unrealistic (most JARs
have a META-INF/MANIFEST.MF), this speed-up will translate to a few
places - such as when loading classes from potentially-signed JAR files.

Testing: tier1-2

Thanks!

/Claes