Add support for VLAN Stacking/Translation API

[kuanyu99]

• Define SAI layer VLAN translation and VLAN Stacking function API in saivlan.h

Use cases: https://github.com/Azure/SONiC/blob/f7920604b77525bd8a13432214fd8d4a5423933c/doc/vlan_stacking/vlan_stacking_HLD.md#vlan-stacking-deployment-use-cases

Examples: https://github.com/Azure/SONiC/blob/f7920604b77525bd8a13432214fd8d4a5423933c/doc/vlan_stacking/vlan_stacking_HLD.md#sai-api

[itaibaz]

Should we also extend saiacl.h to allow pop / swap ? We have SAI_ACL_ACTION_TYPE_ADD_VLAN_ID (push) and set outer/inner vlan ID (swap use case) But I don't see remove_vlan (pop)

[rlhui]

Need to have a SAI specific doc for this. And also describe how this fits to SAI behavioral model.

[kuanyu99]

Need to have a SAI specific doc for this. And also describe how this fits to SAI behavioral model.

I add a document about this new PR and also add a vlan stack stage into the pipeline. I have some problem editing the vsdx file. So I use a PDF to represent the pipeline model about the vlan stacking.

[kcudnik]

please fix errors:

WARNING: not expected number of spaces after * (1,4,8) saivlan.h 561:     *   outer vlan tag, the original one is an inner vlan tag.
WARNING: Long brief > 200 on SAI_VLAN_STACK_ATTR_MATCH_TYPE:
 - Match type The original Vlan ID should match to inner ta...

[kuanyu99]

Hi @rlhui @ashutosh-agrawal @itaibaz @kcudnik , Can we merge this PR? Or what should I do to proceed it?

[kcudnik]

please wait for others to apprive

[kuanyu99]

Hi @ashutosh-agrawal @srj102 @prvattem I have made some updates based on the comments recently. Please check if anything needs to be corrected or can we let the PR be merged.