[Stack Monitoring] use CCS constant in place of '*' string

[neptunian]

As part of #120384 (comment), instead of making CCS remotes customizable via kibana config we will continue to use '*', but place it in a constant. See #129806 for original PR using kibana config. Also adds some other cleanup changes

• Replace usage of * with CCS_REMOTE_PATTERN. This is used by rule executors and getting initial cluster information from the UI to check for remote clusters.
• Remove getConfigCcs and directly access config. We don't need to check of ccs is enabled before using the ccs string value of the remote name/pattern because that already happens in prefixIndexPattern
• change prefixIndexPattern to prefixIndexPatternWithCcs. Previously this was used to also append metricbeat-* to the index but now only handles CCS

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)

[kibana-ci]

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Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
monitoring	471.1KB	471.1KB	-11.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
monitoring	23.7KB	23.7KB	+43.0B

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @neptunian

[matschaffer]

LGTM! As you mentioned we don't have a good way to get SM UI via CCS, so I just confirmed via local monitoring and confirmed that the collected APM traces included the *: prefix.