Adds empty indexer, mapper, metadata, runner, search classes and crea…

[dbbaughe]

…tes high level index management runner that delegates to sub runner

Issue #, if available:

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov]

Codecov Report

Merging #324 (a2e7fc5) into master (2217c5c) will increase coverage by 0.38%.
The diff coverage is 81.96%.

@@             Coverage Diff              @@
##             master     #324      +/-   ##
============================================
+ Coverage     73.94%   74.33%   +0.38%     
- Complexity     1170     1188      +18     
============================================
  Files           174      180       +6     
  Lines          5937     5996      +59     
  Branches        898      900       +2     
============================================
+ Hits           4390     4457      +67     
+ Misses         1082     1071      -11     
- Partials        465      468       +3     

Impacted Files	Coverage Δ	Complexity Δ
...ticsearch/indexmanagement/IndexManagementRunner.kt	37.50% <37.50%> (ø)	2.00 <2.00> (?)
...arch/indexmanagement/rollup/RollupMapperService.kt	50.00% <50.00%> (ø)	1.00 <1.00> (?)
...arch/indexmanagement/rollup/RollupSearchService.kt	66.66% <66.66%> (ø)	1.00 <1.00> (?)
...asticsearch/indexmanagement/rollup/RollupRunner.kt	92.30% <92.30%> (ø)	12.00 <12.00> (?)
...ticsearch/indexmanagement/IndexManagementPlugin.kt	91.81% <93.75%> (+0.15%)	9.00 <1.00> (ø)
...sticsearch/indexmanagement/rollup/RollupIndexer.kt	100.00% <100.00%> (ø)	1.00 <1.00> (?)
...ch/indexmanagement/rollup/RollupMetadataService.kt	100.00% <100.00%> (ø)	1.00 <1.00> (?)
...nt/indexstatemanagement/model/destination/Slack.kt	40.90% <0.00%> (-13.64%)	2.00% <0.00%> (-2.00%)
...exstatemanagement/model/destination/Destination.kt	46.75% <0.00%> (-3.90%)	9.00% <0.00%> (ø%)
...ndexstatemanagement/IndexStateManagementHistory.kt	75.96% <0.00%> (-1.93%)	27.00% <0.00%> (-1.00%)
... and 9 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 2217c5c...25a35b2. Read the comment docs.