[foreign-jextract] [Rev 01] RFR: 8241925: jextract should generate simple allocation, access API for C primitive types

[Athijegannathan Sundararajan]

> added static method helper classes to handle allocation, access ot C primitive types and C strings.

Athijegannathan Sundararajan has updated the pull request incrementally with one additional commit since the last
revision:

  * added static modifier to Cstring.toString method. Added tests for Cstring methods
  * added length accepting allocateArray overloadeds and using the same in samples.
  * using bulk copy for array copy
  * fixed samples to use Cstring method instead of methods from Foreign.

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Changes:
  - all: https://git.openjdk.java.net/panama-foreign/pull/78/files
  - new: https://git.openjdk.java.net/panama-foreign/pull/78/files/258f3e28..4bbec8bd

Webrevs:
 - full: https://webrevs.openjdk.java.net/panama-foreign/78/webrev.01
 - incr: https://webrevs.openjdk.java.net/panama-foreign/78/webrev.00-01

  Stats: 250 lines in 7 files changed: 57 ins; 19 del; 174 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/78.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/78/head:pull/78

PR: https://git.openjdk.java.net/panama-foreign/pull/78