CI: pulling SPGWU image from local private repository

fix(ci): UPF-VPP tutorials are fixed after UPF-VPP configuration has changed

Fixed VPP-UPF tutorial for internet access.

no more mounted healthchecks on NF

Fixes post-v1.4-release

* All official images produced by CI are pushed to `oaisoftwarealliance` Docker-Hub Team account
* New tutorial:
  - My5gRAN Tester --> `docs/DEPLOY_SA5G_WITH_My5g-RANTester.md`
* Update the helm charts and helm chart tutorial
* Reduce image size for all network functions
* New wiki page to know more about variable which can be configured for each network function
* Fix HTTP/2 support for all network functions `docker-compose/docker-compose-basic-nrf-httpv2.yaml`
* `AMF` Changes:
  - Fix SCTP NG Shutdown issue
  - Fix 100% CPU consumption issue
  - Fix RAN UE ID display
  - Fix issue for TMSI and GUTI value
  - Fix for handling S-NSSAI 
  - Remove OPC value from AMF configuration
  - Support for Ubuntu 20.04 bare-metal installation
* `AUSF` Changes:
  - Remove unused packages
  - HTTP/2 support for SBI interface
  - NRF Registration and heartbeat exchange
* `NRF` Changes:
  - Remove unused packages
  - Add NF profile handling for PCF
  - HTTP/2 support for SBI interface
* `NSSF` Changes:
  - Network slice selection for UE registration 
  - NS-AVAIBALITY API support to CREATE new slice
  - Fix bare-metal setup configuration management
  - HTTP/2 support for SBI interface
* `SMF` Changes:
  - Fix for handling S-NSSAI 
  - Add support for IMS
  - HTTP/2 support for SBI interface
  - Add usage report feature
  - Flexiable MTU
  - Support for Ubuntu 20.04 bare-metal installation
* `UDM` Changes:
  - Fix HTTP/2 support
  - NRF Registration and heartbeat exchange
* `UDR` Changes:
  - Fix sync failure issue
  - Fix issue to support Slice Selection Subscription Data retrieval
  - NRF Registration and heartbeat exchange
* `SPGWU-TINY` Changes:
  - Fix for handling S-NSSAI 
  - Add support for multiple slices via config file
  - Allowed reusing GTPv1-U socket
  - Fix GTPU offset sequence number
  - Fix configurable number of DL threads for data path
* `UPF-VPP` Changes:
  - Standalone support validated for traffic steering and redirection
  - Added instructions for bare-metal installation
  - Support for Ubuntu 20.04 bare-metal/docker installation
* `NEF` It is ongoing so far it is not functional

Fixing slicing tutorial for CI test

new infra

Update on the VPP-UPF tutorial

Adding utility traffic-gen image to all docker-compose files

Adding Minimalist Tutorial to automated check test-suite

VPP docker-compose updates

CI Fixes for gnbsim and NSSF; Update UDM info; Fix core-network typo

CI: adding slicing tutorial to automated check and PCAP captures for all tutorials

CI: adding tutorial check pipeline

2021-Q4 Milestone:

* Incorporation of new public network functions:
  - NSSF
* New tutorials:
  - Slicing --> `docs/DEPLOY_SA5G_SLICING.md`
  - Static UE IP address to emulate private network --> `docs/DEPLOY_SA5G_BASIC_STATIC_UE_IP.md`