feat(develop): Document indexed outcome categories

develop-docs/application/dynamic-sampling/outcomes.mdx

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+---
+title: The “Indexed” Outcome Category
+sidebar_order: 4
+---
+
+Data types which are subject to dynamic sampling are represented in two different outcome data categories: "total" and "indexed". You can think of the "total" category as counting items that are stored in _aggregated_ form, in other words, as metrics. The "indexed" category counts items that are stored individually.
+
+If an item is dropped _before_ metrics extraction & dynamic sampling, it will show up as an outcome in both categories (for example, `"transaction"`  and `"transaction_indexed"`). If an item is dropped _by_ dynamic sampling, it will show up as a "filtered" outcome in the "indexed" category, but it lives on in the form of metrics, for which we emit an "accepted" outcome in the "total" category.
+
+## Illustration
+
+These charts illustrate the flow of data categories for transactions:
+
+For a sampled transaction:
+
+![](https://mermaid.ink/img/pako:eNp1UT1vgzAQ_SvWzYAgJoA9ZGJru4StdVWdwCGWwI4c04Yi_nsNDI2U1l589z58TzdBbRoJHE6d-arPaB15PgpN_KnKJxKGzqK-Yu2U0WF4IEfZ4bjh6_ORUVZv5aixVzWpsL90Srfv_wo-lG7kTTabcKOV1YNp5YyVf6N3DncsoZcLAfTS9qgaH3BaEPGbUwAnk2_Ug_2USyHAzyrRCiCz0LMX4-BMNeoauLODDGC4NOhkqbC12AM_YXf13Qtq4BPcgCcJi2gRs13BaLYvkl0RwAg8zVjEWBonOaVZwWI6B_BtjHeIo32esyyOk5SmdJcleQCyUT7Hy7aVdTkBWDO05_sPX1f5MtX8Azhkjhw)
+
+For a transaction filtered by dynamic sampling:
+
+![](https://mermaid.ink/img/pako:eNp1UcFSgzAQ_ZXMeoVOaCiQHDxxUy_lpnGcDGzbKCSdNGiR4d8N5WBnqskl-_a9t9ndEWrbIAjYtfarPijnyeNWGhJOVT6QOPZOmZOqvbYmju_JFls1LPnL85ZRVi_lYFSna1Kp7thqs3_9V_CmTYNnbBbhQiurG9PKW4d_Z68ctviOtV9oJz-0SBYkBM5-oLjbUSrNfCGCDl2ndBM6H2eF_B2ABEHGANS9-8Q5kBCaQOUkkEmaKYhV7201mBqEdz1G0B8b5bHUau9UB2Kn2lNAj8qAGOEMIkn4ihWUrwvOsk2RrIsIBhBpxlecpzTJGcsKTtkUwbe1wYGuNnnOM0qTlKVsnSV5BNjoMIanZV2XrUXgbL8_XBd8vsjnX00_t7aW9Q)
+
+## Data Types
+
+The following data categories have a corresponding `"*_indexed"` category:
+
+* transactions
+* spans
+* profiles