There are a lot of calls to `Metrics.id()` and `ISource.getEntityId`, which calculates the id by manipulating strings in every single call, producing many garbage objects.

In this patch, I cache the id and only calculate the id if it's requested for the first time.

The possible metrics names are relatively fixed in an OAP run, we previously always escape the metrics names, building a new regex Pattern from scratch, which is cpu-consuming.

In this patch, I cache the escaped metrics names, and if it missed, use a pre-compiled regex Pattern to escape the metrics name.

This patch also replace string concatenation `+` with `StringBuilder` in generated classes, which won't get optimized by Java compiler

This may reduce 1~1.5 vCPU under 20K RPS environment.

These fields in `stateMap` metadata are not used by `metadata-service-mapping.yaml` now and there is low possibility that they may be used in real case, but, they cost a lot to deserialize, so we remove them to improve performance

From what I've tested, the analyzer can process 250k ALS logs before trimming the fields and can process 420k ALS logs after trimming the fields

Perf: optimize Envoy ALS analyzer performance in high traffic load scenario (reduce ~1cpu in ~10k RPS) (#7182)

* OAL supports generating metrics from events

* Add new dashboard for event metrics

* Add some docs for event metrics

* Introduce trivy to scan images
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>

* Fix CVE
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>

* Update licenses
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>

* Remove log4j 1.x
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>

* Update CHANGES.md
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>

* Update LICENSE refer to webapp
Signed-off-by: NGao Hongtao <hanahmily@gmail.com>
Co-authored-by: 吴晟 Wu Sheng <wu.sheng@foxmail.com>

* polish debug logging avoid null value.

* update CHANGES.md.