Fix index.mapping.use_doc_values_skippers defaults in serverless

[romseygeek]

We can't detect whether or not we are in serverless during default value
setup because we don't have node settings at this point. This removes
all serverless/stateful detection logic from here, as the various different
index structure changes made during development were never released
and we can use some much simpler checks.

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)

[elasticsearchmachine]

Hi @romseygeek, I've created a changelog YAML for you.

[martijnvg]

LGTM

[salvatore-campagna]

Question: I was looking into this issue and noticed that the DiscoveryNode.isStateless(s) calls in the default function might never have worked because s is index settings but stateless.enabled is a NodeScope setting. Is that the root cause here?

Also, do we need any stateless-specific handling elsewhere (like in the IndexSettings constructor using nodeSettings)? I'm thinking of the pattern we use for recoverySourceSyntheticEnabled. Just want to make sure we're not missing something for the timestamp case.

[romseygeek]

Is that the root cause here?

Yes, exactly. We should be fine elsewhere as nothing here has actually been released - it's all post-9.2 or behind a feature flag.

[jordan-powers]

I confirmed that the same test fails on this PR as in the serverless-fix PR #139532.

Reproduce with:

./gradlew :x-pack:plugin:logsdb:qa:rolling-upgrade:bcUpgradeTest -Dtests.class="org.elasticsearch.xpack.logsdb.RandomizedRollingUpgradeIT" -Dtests.method="testIndexingStandardSource" -Dtests.bwc.main.version=9.3.0-SNAPSHOT -Dtests.bwc.refspec.main=31d034824763bd0c6e76f0e282a9241f11a9b3ed -Dtests.seed=DF23618074EC7280 --info

The error:

java.lang.AssertionError: errors in bulk response:
     {took=0, items=[{create={_index=test-index-standard-0, _id=16, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={_index=test-index-standard-0, _id=17, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={_index=test-index-standard-0, _id=18, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={_index=test-index-standard-0, _id=19, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={_index=test-index-standard-0, _id=20, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={_index=test-index-standard-0, _id=21, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}, {create={result=created, _shards={total=2, failed=0, successful=1}, _seq_no=22, _index=test-index-standard-0, forced_refresh=true, _id=22, _version=1, _primary_term=3, status=201}}, {create={_index=test-index-standard-0, _id=23, error={reason=cannot change field "ruLbCWwiEg.oTzMzhQGD" from docValuesSkipIndexType=RANGE to inconsistent docValuesSkipIndexType=NONE, type=illegal_argument_exception}, status=400}}], errors=true}
    Expected: <false>
         but: was <true>
        at __randomizedtesting.SeedInfo.seed([DF23618074EC7280:821DDC7665512016]:0)
        at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:20)
        at org.elasticsearch.test.ESTestCase.assertThat(ESTestCase.java:2813)
        at org.elasticsearch.xpack.logsdb.RandomizedRollingUpgradeIT.indexDocuments(RandomizedRollingUpgradeIT.java:166)
        at org.elasticsearch.xpack.logsdb.RandomizedRollingUpgradeIT.testIndexing(RandomizedRollingUpgradeIT.java:123)
        at org.elasticsearch.xpack.logsdb.RandomizedRollingUpgradeIT.testIndexingStandardSource(RandomizedRollingUpgradeIT.java:133)

The problem is that at the index version STANDARD_INDEXES_USE_SKIPPERS (which is the latest index version in serverless right now), skippers are enabled by default in snapshot builds. But after this PR, the setting is disabled by default. I added eff7223 to fix the other PR, we might consider something similar here.