Support inject bootstrap-plugins by swck.

[weixiang1862]

swck now support inject optional-plugins and optional-report-plugins by SwAgent CRD or workload annotations. I want add supporting for bootstrap-plugins:

SwAgent

apiVersion: operator.skywalking.apache.org/v1alpha1
kind: SwAgent
...
  optionalPlugins:
    - "webflux"
  bootstrapPlugins:          <-------------
    - "threadpool"

workload annotation

apiVersion: apps/v1
kind: Deployment
spec:
  selector:
    matchLabels:
      app: demo
  template:
    metadata:
      annotations:
        optional.skywalking.apache.org: "webflux"
        bootstrap.skywalking.apache.org: "threadpool"        <-------------

[wu-sheng]

@dashanji Please take a look.

[dashanji]

@weixiang1862 Thanks for the proposal, it looks good. Could you please submit a PR to address this?

[weixiang1862]

Ok, thanks. I will submit pr later.

[wu-sheng]

Codes are apache/skywalking-swck#91