* [APM] Always get the root transaction when fetching trace items
Fixes#33210
* code tweaks
* displays message notifying user that trace items exceeds maximum displayed
* remove getTraceRoot query by adjusting the score and order of trace
items with no parent.id
* add `apm_oss.maxTraceItems` config options to control the number of displayed trace items
* changed config `apm_oss.maxTraceItems` to `xpack.apm.ui.maxTraceItems`
* added missing configs to apm settings doc and docker template
* minor code tweak
* [APM] Fixes#24204 by adding default configs to kibana.yml
* [APM] fixes#25940 by adding APM config to control top transation group agg size
* Revert the default configs added to kibana.yml and define joi validations for `xpack.apm.ui.transactionGroupBucketSize`
* fix broken test for incorrect config
* [APM] add docs entry for `xpack.apm.ui.transactionGroupBucketSize`
GitHub's asciidoc parser handles `*` characters fine but markdown thinks its italicizing unless you escape the first asterisk. Subsequent asterisks on the same line can stay unescaped and should work fine.
