fix or remove ecj linter, jtidy, etc? [LUCENE-6230]

We now have doclint running on compile/javadoc to find problems. Can we remove some extra linters?

Jtidy: this consumes a ton of memory, and doesn't have good error messages. Can we just remove it in trunk at least?

ECJ: this is slow, unless we upgrade minimum ant version from 1.8.2 to 1.8.3, then we can make it _really_ not generate .class files, because the javac task has a createMissingPackageInfoClass we can disable. alternatively, we could also remove this checker. I am unsure if its providing anything beyond doclint.

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Migrated from [LUCENE-6230](https://issues.apache.org/jira/browse/LUCENE-6230) by Robert Muir (@rmuir)
Attachments: [LUCENE-6230_fix_ecj_increase_ant.patch](https://apache.github.io/lucene-jira-archive/attachments/LUCENE-6230/LUCENE-6230_fix_ecj_increase_ant.patch)

Start by reviewing the build configuration for the compile/javadoc doclint task and the Jtidy and ECJ checks described in the issue. Read the attached LUCENE-6230_fix_ecj_increase_ant.patch for prior context, then compare what each checker still reports beyond doclint. Done means an agreed decision is implemented and the build remains passing without unnecessary checks.

Written by the indexing model from the issue text.