[PURIFY] Remove `Default` distribution and only create OSS distribution.

The Default distribution is governed by Elastic license and hence needs to be removed and only create OSS distribution.

Clean up distribution (@setiah)

• Clean up non OSS distributions in Docker. - https://github.com/opendistro-for-elasticsearch/search/blob/main/distribution/docker
• Clean up non OSS flavors in Elasticsearch Distributions. - https://github.com/opendistro-for-elasticsearch/search/blob/main/buildSrc/src/main/java/org/elasticsearch/gradle/ElasticsearchDistribution.java#L77
• Clean up non OSS flavors in packaging - https://github.com/opendistro-for-elasticsearch/search/tree/main/distribution/packages
• Clean up UBI Docker flavor - @saratvemulapalli

PR: #102 #103 #110

Test with failures

• DistributionDownloadPluginFuncTest. bwc version can be resolved
• DistributionDownloadPluginFuncTest. current version can be resolved
• DistributionDownloadPluginFuncTest. released version can be resolved
• DistributionDownloadPluginFuncTest. transformed versions are kept across builds
• DistributionDownloadPluginFuncTest. transforms are reused across projects
• TestClustersPluginFuncTest. custom distro folder created for tweaked cluster distribution
• TestClustersPluginFuncTest. test cluster distribution is configured and started
• InternalDistributionBwcSetupPluginFuncTest. builds distribution from branches via archives assemble
• InternalDistributionBwcSetupPluginFuncTest. bwc distribution archives can be resolved as bwc project artifact
• InternalDistributionBwcSetupPluginFuncTest. bwc expanded distribution folder can be resolved as bwc project artifact
• InternalDistributionDownloadPluginFuncTest. resolves current version from local build
• InternalDistributionDownloadPluginFuncTest. resolves expanded bwc versions from source

Remove Flavor Enums (@adnapibar)

• remove the Flavor support
• remove -oss flag dependencies in package and build tests

PR: #104

Test with failures

./gradlew ':qa:rolling-upgrade:v6.8.15#oneThirdUpgradedTest'

• org.elasticsearch.upgrades.IndexingIT.testIndexing
• org.elasticsearch.upgrades.RecoveryIT.testUpdateDoc
• org.elasticsearch.upgrades.RecoveryIT.testSoftDeletesDisabledWarning
• org.elasticsearch.upgrades.RecoveryIT.testRelocationWithConcurrentIndexing
• org.elasticsearch.upgrades.RecoveryIT.testAutoExpandIndicesDuringRollingUpgrade
• org.elasticsearch.upgrades.RecoveryIT.testRetentionLeasesEstablishedWhenPromotingPrimary
• org.elasticsearch.upgrades.RecoveryIT.testRecoveryWithConcurrentIndexing
• org.elasticsearch.upgrades.RecoveryIT.testCloseIndexDuringRollingUpgrade

./gradlew ':qa:mixed-cluster:v6.8.15#mixedClusterTest'

• org.elasticsearch.backwards.IndexingIT.testUpdateSnapshotStatus
• org.elasticsearch.backwards.IndexingIT.testIndexVersionPropagation
• org.elasticsearch.backwards.MixedClusterClientYamlTestSuiteIT

Clean up buildSrc (@setiah)

• Remove logic to check the distribution flavor and make the OSS as the only option.

[saratvemulapalli]

Probably we can make this as a meta task. There are references of non-oss code in build script which should be cleaned in packaging. https://github.com/opendistro-for-elasticsearch/search/blob/main/distribution/packages/build.gradle

[adnapibar]

Yes