fix(restheart-mongo): bound JVM heap to prevent OOM on shared CI runners

RESTHeart 9.x's default JVM uses MaxRAMPercentage=25, which on a
typical Woodpecker runner cgroup (~8GB) lands ~2GB heap. With the
keploy/enterprise compat matrix running 3 restheart cells concurrent
alongside parse-server / umami / doccano cells (12 lane-cells total
on one runner), aggregate memory pressure triggers cgroup OOM and
the kernel SIGKILLs lighter processes (bash, curl) mid-bootstrap.

Observed in keploy/enterprise pipeline 3721/26 (record-stable-replay-pr):
RESTHeart came up cleanly (`127.0.0.1:18070 is now reachable`), then
`bash flow.sh bootstrap 240` got SIGKILL'd (exit 137) before any
seed PUTs landed. Same shape across all 3 restheart cells in 3721.

Cap heap at -Xmx512m (start at -Xms128m). Local single-cell
record/replay peaks at ~280MB heap, so 512m is comfortable headroom
without bleeding into neighbours. With the bound, each cell's
footprint stays under ~700MB (heap + native + mongo); 3 restheart
cells fit alongside other lanes on a shared runner.

Validated locally: cell record-pr-replay-pr 296/0 PASSED with the
new JAVA_TOOL_OPTIONS in place. RESTHeart logs confirm
"Picked up JAVA_TOOL_OPTIONS: -Xms128m -Xmx512m ..." at startup.

Author: AkashKumar7902

restheart-mongo/docker-compose.yml

@@ -28,6 +28,22 @@ services:
       # the bearer signature verifiable across record→replay
       # container restarts (deterministic key, deterministic JWT).
       RHO: '/mclient/connection-string->"mongodb://${RESTHEART_MONGO_IP:-172.36.0.10}:27017";/http-listener/host->"0.0.0.0";/core/log-level->"INFO";/jwtConfigProvider/key->"keploy-fixed-jwt-secret-for-deterministic-recordings"'
+      # Bound RESTHeart's JVM heap. RESTHeart 9.x's default uses
+      # `MaxRAMPercentage=25` of cgroup memory, which on a typical
+      # Woodpecker runner cgroup (~8GB) lands ~2GB heap. With three
+      # restheart matrix cells running concurrent on the same
+      # runner alongside parse-server / umami / doccano cells, the
+      # total memory pressure triggers cgroup OOM and the kernel
+      # SIGKILLs lighter processes (bash, curl) mid-bootstrap —
+      # observed in keploy/enterprise pipeline 3721/26 (cell
+      # record-stable-replay-pr) where `flow.sh bootstrap` got
+      # killed (exit 137) right after RESTHeart came up. Capping
+      # heap at 512m keeps each cell's footprint under ~700MB
+      # (heap + native + mongo) so the runner can host all three
+      # restheart cells plus the other lanes' cells in parallel.
+      # 512m is comfortable for the record/replay workload (peak
+      # observed at ~280MB in single-cell local runs).
+      JAVA_TOOL_OPTIONS: "-Xms128m -Xmx512m"
     depends_on:
       mongo:
         condition: service_healthy