RFR: Save/load i2c2i adapters

[Ashutosh Mehra]

This is an attempt to save and load i2c2i adapters along with the adapter handler table.
There are mainly two parts to this change:
1. Storing of adapter code in the SCCache or AOT code cache.
2. Storing of adapter handler table in the AOT cache.

Adapter handler table is a map from AdapterFingerPrint to AdapterHnadlerEntry. To store them in AOT cache, AdapterFingerPrint and AdapterHandlerEntry are updated to MetaspaceObj. Both these entities are discovered and added to the cache while processing the Method. When storing the adapter handler table, only the entries that have already been archived are considered. This allows pruning of AdapterHnadlerEntry that may be only reachable through a Method that is not eligible to be archived. 

An AdapterHandlerEntry has pointer to the adapter code. Because the AdapterHandlerEntry and the adapter code are stored in separate archives, this link between the AdapterHandlerEntry and the adapter code needs to be removed (see AdapterHandlerEntry::remove_unshareable_info()).
During the production run, as the methods in the AOT cache are adopted, the AdapterHandlerEntry is linked back to the adapter code (see AdapterHandlerEntry::restore_unshareable_info).

All this code is guarded by -XX:[+-]ArchiveAdapters option which defaults to false, but is set to true in CDSConfig during the assembly phase.

Other changes worth mentioning:
1. Changes to the SCCache infrastructure to make it possible to store and load adapter code. (Thanks to @adinn)
2. Updating AdapterFingerPrint hashing algorithm to avoid collisions. If there is any collision, then it will prevent finding the adapter code in the SCCache. (Again courtesy of @adinn)

Thanks to @adinn for providing many of these changes.

Performance:
-Xlog:init shows time taken for linking of Methods and making adapters. An example output is:

ClassLoader:
  clinit:                             150us / 4612 events
  link methods:                     28980us / 176893 events
  method adapters:                  15378us / 697 events

Save/load of adapters seem to have improved these stats.

| Quarkus | -ArchiveAdapters | +ArchiveAdapters |
|---|---|---|
| link methods | 12214us / 58913 events | 2700us / 58913 events |
| method adapters | 7793us / 607 events | 4402us / 38 events |

| Spring-petclinic | -ArchiveAdapters | +ArchiveAdapters |
|---|---|---|
| link methods | 28980us / 176893 events | 7485us / 176893 events |
| method adapters | 15378us / 697 events | 7050us / 13 events |

However, testing with Quarkus app, I don't see any noticeable improvement in the startup time.

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Commit messages:
 - More whitespace fixes
 - Move the check for is_abstract_method_adapter() to correct place
 - Surround code with INCLUDE_CDS where appropriate
 - Fix whitespace issues
 - Fix compile failures
 - Fix a bug and add comment in AdapterHandlerEntry::restore_unshareable_info()
 - Refactor code to avoid calling AdapterFingerPrint::as_basic_type() when
 - Add a helper method to iterate over AdapterFingerPrint
 - Improve hashing algorithm for AdapterFingerPrint
 - Misc changes
 - ... and 10 more: https://git.openjdk.org/leyden/compare/a1672ea6...04fb256b

Changes: https://git.openjdk.org/leyden/pull/25/files
  Webrev: https://webrevs.openjdk.org/?repo=leyden&pr=25&range=00
  Stats: 1293 lines in 25 files changed: 834 ins; 248 del; 211 mod
  Patch: https://git.openjdk.org/leyden/pull/25.diff
  Fetch: git fetch https://git.openjdk.org/leyden.git pull/25/head:pull/25

PR: https://git.openjdk.org/leyden/pull/25