RFR: 8272773: Investigate making card table size configurable

[Vishal Chand]

Hi,

Please review the changes to make CardTable entry size configurable. The changes primarily consists of:

1. Addition of a cmdline flag **GCCardSizeInBytes** to make the card size startup time configurable.
2. Setting the card size based on the flag in G1, Parallel and Serial GC memory initialization paths.
3. Setting BlockOffsetTable size and ObjectStartArray size based on the card size.

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Commit messages:
 - 8272773: Investigate making card table size configurable

Changes: https://git.openjdk.java.net/jdk/pull/5838/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5838&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8272773
  Stats: 109 lines in 10 files changed: 87 ins; 1 del; 21 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5838.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5838/head:pull/5838

PR: https://git.openjdk.java.net/jdk/pull/5838