mzbench: remove

mzbench has been obsoleted by the feature benchmark framework (in
test/feature-benchmark) and the cloudbench tool (bin/cloudbench).  The
kafka-avro-generator tool has been obsoleted by parallelizing kgen
directly (#9841). So this commit removes mzbench.

To expound on the rational for removing mzbench:

  * mzbench configurations require an unmaintainable duplication of
    mzcompose.yml files. Each mzbench configuration contains 300+ lines of
    nearly identical definitions. There was talk of improving this (see
    #6676), but the plans never came to fruition.

  * The interplay between mzbench and mzcompose is unnecessarily
    delicate. mzbench expects a composition with workflows named just
    so, and then parses their output. This makes it very difficult to
    refactor the underlying compositions, since you don't know if you're
    breaking the contract with mzbench. I think most of mzbench's
    features could be recreated much more simply with an e.g.
    `--num-trials` parameter to mzcompose.

  * mzbench introduced quite a bit of complexity by trying to be both a demo
    of using Materialize to power a real-time dashboard [0] and a
    benchmarking framework. Experience suggests that this results in a
    tool that is a suboptimal dashboard and a suboptimal benchmarking
    framework. Better to have two separate tools optimized for their
    specific purpose.

The new feature benchmarking framework resolves the above concerns. It
is only focused on being a benchmarking framework and does not suffer
from the code duplication problem.

[0]: https://github.com/MaterializeInc/materialize/blob/45586f38a/doc/developer/mzbench.md#worker-balance-visualization

Author: benesch

bin/mzbench

@@ -162,30 +162,6 @@ steps:
           run: ci
     timeout_in_minutes: 30
 
-  - label: "aggregations benchmark sanity check"
-    depends_on: build-x86_64
-    plugins:
-      - ./ci/plugins/mzcompose:
-          composition: aggregations
-          run: ci
-    timeout_in_minutes: 10
-
-  - label: "avro upsert benchmark sanity check"
-    depends_on: build-x86_64
-    plugins:
-      - ./ci/plugins/mzcompose:
-          composition: avro-upsert
-          run: ci
-    timeout_in_minutes: 10
-
-  - label: "kafka sink (avro debezium) benchmark sanity check"
-    depends_on: build-x86_64
-    plugins:
-      - ./ci/plugins/mzcompose:
-          composition: kafka-sink-avro-debezium
-          run: ci
-    timeout_in_minutes: 10
-
   - label: ":book: catalog compatibility check"
     depends_on: build-x86_64
     timeout_in_minutes: 30