[DISCUSSION] Code style. Variable abbrevations

[Nikolay Izhikov]

Hello, Igniters.

Right now, we have the rule to use some predefined list of abbrevation for 
variable names [1].
Some of the reviewers ask to follow this rule strictly.

> It is required to use abbreviated form for code consistency.

I tried to implement this rule in form of checkstyle check [2] and it seems 
like many of use doesn’t follow this requirement.
My check found 4124 violation in core module.

Should we make this rule optional in documentation or should we remove it 
completely?
Or should someone proceed and fix all the violations?

WDYT?


Example of output:
```
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsWithTtlTest.java:94:
 Abbrevation should be used for CACHE_NAME_LOCAL_ATOMIC! Please, use loc, 
instead of LOCAL [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsWithTtlTest.java:97:
 Abbrevation should be used for CACHE_NAME_LOCAL_TX! Please, use loc, instead 
of LOCAL [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsWithTtlTest.java:264:
 Abbrevation should be used for checkpointManager! Please, use mgr, instead of 
Manager [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsPartitionPreloadTest.java:63:
 Abbrevation should be used for DEFAULT_REGION! Please, use dflt, instead of 
DEFAULT [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsWholeClusterRestartTest.java:47:
 Abbrevation should be used for ENTRIES_COUNT! Please, use cnt, instead of 
COUNT [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsRebalancingOnNotStableTopologyTest.java:49:
 Abbrevation should be used for CHECKPOINT_FREQUENCY! Please, use freq, instead 
of FREQUENCY [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsTransactionsHangTest.java:75:
 Abbrevation should be used for MAX_KEY_COUNT! Please, use cnt, instead of 
COUNT [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgnitePdsTransactionsHangTest.java:78:
 Abbrevation should be used for CHECKPOINT_FREQUENCY! Please, use freq, instead 
of FREQUENCY [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/SlowHistoricalRebalanceSmallHistoryTest.java:57:
 Abbrevation should be used for SUPPLY_MESSAGE_LATCH! Please, use msg, instead 
of MESSAGE [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgniteLogicalRecoveryTest.java:74:
 Abbrevation should be used for SHARED_GROUP_NAME! Please, use grp, instead of 
GROUP [IgniteAbbrevationsRule]
[ERROR] 
/Users/sbt-izhikov-nv/work/ignite/modules/core/src/test/java/org/apache/ignite/internal/processors/cache/persistence/db/IgniteLogicalRecoveryTest.java:200:
 Abbrevation should be used for cacheLoader! Please, use ldr, instead of Loader 
[IgniteAbbrevationsRule]
```

[1] 
https://cwiki.apache.org/confluence/display/IGNITE/Abbreviation+Rules#AbbreviationRules-VariableAbbreviation
[2] https://github.com/apache/ignite/pull/9153