[vslib] SAI_KEY_VS_OPER_SPEED_IS_CONFIGURED_SPEED, SAI_PORT_ATTR_HOST_TX_READY_STATUS support

[ishidawataru]

This PR adds two features to vslib.

• SAI_KEY_VS_OPER_SPEED_IS_CONFIGURED_SPEED: when true, SAI_PORT_ATTR_SPEED returns the configured speed instead of the value retrieved via /sys/class/net/<name>/speed.

  • fixes Subinterface doesn't inherit the speed of ancestors on kvm testbed.  sonic-buildimage#19735

• SAI_PORT_ATTR_HOST_TX_READY_STATUS: always returns true. Required to support running xcvrd in the VS env.

  • ref: https://github.com/sonic-net/SONiC/pull/1849/files#diff-6f3e95e6c57a3edc2e30e1f13edb9fd9a32a0db44e1035ac1f0b1b9a191762a5R46

[kcudnik]

this name is a little bit confusing, it suggest that this is a question or value to read and not an config value

why we need this actually ?

also does this only applies when tap device is in use?

[ishidawataru]

this name is a little bit confusing,

How about SAI_KEY_VS_USE_CONFIGURED_SPEED_AS_OPER_SPEED?

why we need this actually ?

I'm testing DPB on the VS environment.
To check that DPB is working as expected, it'd be nice to see the show interface status command shows the expected interface speed.

admin@sonic:~$ show interface status
  Interface    Lanes    Speed    MTU    FEC    Alias    Vlan    Oper    Admin                                             Type    Asym PFC
-----------  -------  -------  -----  -----  -------  ------  ------  -------  -----------------------------------------------  ----------
  Ethernet0  1,2,3,4     400G   9100    N/A   Eth0/0  routed    down     down  QSFP-DD Double Density 8X Pluggable Transceiver         N/A
admin@sonic:~$ sudo config interface breakout Ethernet0 "2x200G"
Do you want to Breakout the port, continue? [y/N]: y

Running Breakout Mode : 1x400G 
Target Breakout Mode : 2x200G

Ports to be deleted : 
 {
    "Ethernet0": "400000"
}
Ports to be added : 
 {
    "Ethernet0": "200000",
    "Ethernet2": "200000"
}
Breakout process got successfully completed.
Please note loaded setting will be lost after system reboot. To preserve setting, run `config save`.
admin@sonic:~$ show interface status
  Interface    Lanes    Speed    MTU    FEC    Alias    Vlan    Oper    Admin                                             Type    Asym PFC
-----------  -------  -------  -----  -----  -------  ------  ------  -------  -----------------------------------------------  ----------
  Ethernet0      1,2     200G   9100    N/A   Eth0/0  routed    down     down  QSFP-DD Double Density 8X Pluggable Transceiver         N/A
  Ethernet2      3,4     200G   9100    N/A   Eth0/1  routed    down     down                                              N/A         N/A

also does this only applies when tap device is in use?

I don't think so. SwitchStateBase::refresh_port_oper_speed doesn't care SAI_VS_HOSTIF_USE_TAP_DEVICE configuration.

[kcudnik]

Changed name looks good

[ishidawataru]

fixed