Add podSpec to generated environment manifest

[soharab-ic]

Description

• Add podSpec to generated environment manifest file. This will help user utilize the podSpec fields for thier enviroment.
• With this change, user can easily set nodeSelector, add sidecar containers etc. to environment pods.

New environment manifest:

$ fission env create --name go --image ghcr.io/fission/go-env --builder ghcr.io/fission/go-builder --dry
apiVersion: fission.io/v1
kind: Environment
metadata:
  creationTimestamp: null
  name: go
spec:
  builder:
    command: build
    container:
      name: builder
      resources: {}
    image: ghcr.io/fission/go-builder
    podspec:
      containers:
      - name: builder
        resources: {}
  imagepullsecret: ""
  keeparchive: false
  poolsize: 3
  resources: {}
  runtime:
    container:
      name: go
      resources: {}
    image: ghcr.io/fission/go-env
    podspec:
      containers:
      - name: go
        resources: {}
  version: 3

Old environment manifest:

$ fission env create --name go --image ghcr.io/fission/go-env --builder ghcr.io/fission/go-builder --dry
apiVersion: fission.io/v1
kind: Environment
metadata:
  creationTimestamp: null
  name: go
spec:
  builder:
    command: build
    container:
      name: ""
      resources: {}
    image: ghcr.io/fission/go-builder
  imagepullsecret: ""
  keeparchive: false
  poolsize: 3
  resources: {}
  runtime:
    container:
      name: ""
      resources: {}
    image: ghcr.io/fission/go-env
  version: 3

Which issue(s) this PR fixes:

Fixes #2786

Testing

• Add sidecar containers to builder and runtime pods.
• Using invalid builder and runtime container names either in containerSpec or podSpec or both places will not create builder and runtime deployments.

Checklist:

• I ran tests as well as code linting locally to verify my changes.
• I have done manual verification of my changes, changes working as expected.
• I have added new tests to cover my changes.
• My changes follow contributing guidelines of Fission.
• I have signed all of my commits.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 45.97%. Comparing base (fe7f1b0) to head (ad0f158).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3033      +/-   ##
==========================================
+ Coverage   45.85%   45.97%   +0.11%     
==========================================
  Files         236      236              
  Lines       19566    19580      +14     
==========================================
+ Hits         8972     9001      +29     
+ Misses       9190     9177      -13     
+ Partials     1404     1402       -2     

Flag	Coverage Δ
unittests	45.97% <100.00%> (+0.11%)	⬆️

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