Remove code and test to generate flamegraph on GetPage requests. (#3257)

It was nice to have and useful at the time, but unfortunately the method
used to gather the profiling data doesn't play nicely with 'async'. PR
#3228 will turn 'get_page_at_lsn' function async, which will break the
profiling support. Let's remove it, and re-introduce some kind of
profiling later, using some different method, if we feel like we need it
again.

.github/workflows/build_and_test.yml

@@ -183,13 +183,12 @@ jobs:
       # corresponding Cargo.toml files for their descriptions.
       - name: Set env variables
         run: |
+          CARGO_FEATURES="--features testing"
           if [[ $BUILD_TYPE == "debug" ]]; then
             cov_prefix="scripts/coverage --profraw-prefix=$GITHUB_JOB --dir=/tmp/coverage run"
-            CARGO_FEATURES="--features testing"
             CARGO_FLAGS="--locked $CARGO_FEATURES"
           elif [[ $BUILD_TYPE == "release" ]]; then
             cov_prefix=""
-            CARGO_FEATURES="--features testing,profiling"
             CARGO_FLAGS="--locked --release $CARGO_FEATURES"
           fi
           echo "cov_prefix=${cov_prefix}" >> $GITHUB_ENV