1. add tables required for the feature:
 - ASIC_TABLE in platform/mellanox/asic_table.j2 (Mellanox specific)
 - PERIPHERAL_TABLE in platform/mellanox/peripheral_table.j2 (Mellanox specific)
 - PORT_PERIPHERAL_TABLE on a per-platform basis in device/mellanox/x86_64-mlnx_msn3800-r0/port_peripheral_config.j2 (Mellanox specific)
 - DEFAULT_LOSSLESS_BUFFER_PARAMETER and LOSSLESS_TRAFFIC_PATTERN in files/build_templates/buffers_config.j2
 - Add lossless PGs (3-4) for each port in files/build_templates/buffers_config.j2
2. copy the newly introduced j2 files into image and rendering them when system starts
3. update the CLI options for buffermgrd so that it can start with dynamic mode
4. Adjust the order in which swss daemons start, making buffermgrd start before orchagent.
   This is to make sure buffermgrd can get everything ready before orchagent starts especially during warm reboot.
5. Optimize the way in which orchagent fetches the asic vendor name:
 - fetch the vendor name when creates the docker and pass it as a docker environment variable
 - orchagent and buffermgrd can use this passed-in variable
6. Clear buffer related tables from STATE_DB when swss docker starts
7. Update the src/sonic-config-engine/tests/sample_output/buffers-dell6100.json according to the buffer_config.j2
8. Remove buffer pool sizes for ingress pools and egress_lossy_pool
   Update the buffer settings for dynamic buffer calculation

Signed-off-by: Stephen Sun <stephens@nvidia.com>

1. If all the buffer configuration aligns the default, use dynamic
buffer calculation mode. Otherwise, use the traditional mode
2. Dynamic mode is adopted in switches newly installed from scratch and
traditional mode in switches installed from ninigraph
This is done by:
- introducing a wrapper to buffermgrd, which enables it to test which
mode is adopted and feed buffermgrd with corresponding CLI arguments
- preparing default buffer configuration templates for both dynamic and
traditional mode for each SKU
- introduce "buffer_model" in DEVICE_METADATA|localhost for mellanox platform

Signed-off-by: Stephen Sun <stephens@nvidia.com>

Signed-off-by: Stephen Sun <stephens@nvidia.com>

- For Mellanox, dynamic by default
- For other vendors, traditional mode.

Signed-off-by: Stephen Sun <stephens@nvidia.com>

Signed-off-by: Stephen Sun <stephens@nvidia.com>

…able

Signed-off-by: Stephen Sun <stephens@nvidia.com>

Signed-off-by: Stephen Sun <stephens@nvidia.com>