This change renames the _timescale_catalog.telemetry_metadata to
_timescale_catalog.metadata. It also adds a new boolean column to this
table which is used to flag data which should be included in telemetry.
It also renamed the src/telemetry/metadata.{h,c} files to
src/telemetry/telemetry_metadata.{h,c} and updated the API to reflect
this. Finally it also includes the logic to use the new boolean column
when populating the telemetry parse state.
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