Control search index's text match scope through (local) latencies.

[isoos]

• Controls both package index (Package search index improvements (tracking issue) #8671) and SDK index (SDK search index improvements (tracking issue) #8670).
• While the changes inside the text search seems a lot, it is mostly the indent change, otherwise only skipping the index matches when the textMatchExtent field does not support it.
• Returns an errorMessage when not even the name index was used. (TBD: more noticeable exposure of such messages)
• Introduces latency tracking with half-life decay of one minute. Considered alternatives: aggregation over last-N-events, last-X-minute, sampling over Y-minutes window.
• This is scoped only at the local index level. To make this consistent across all search instances, we could synchronize such decaying value(s) through redis. TBD in a subsequent PR.
• Note: I've also considered enum or bools for controlling the match extent, but that was more complex without much gain.