To fix [DPB| wrong aliases for interfaces](https://github.com/Azure/sonic-buildimage/issues/6024) issue, implimented flexible alias support [design doc](https://github.com/Azure/SONiC/pull/749)
> [[dpb|config] Fix the validation logic of breakout mode](https://github.com/Azure/sonic-utilities/pull/1440) depends on this
#### How I did it
1. Removed `"alias_at_lanes"` from port-configuration file(i.e. platfrom.json)
2. Added dictionary to "breakout_modes" values. This defines the breakout modes available on the platform for this parent port, and it maps to the alias list. The alias list presents the alias names for individual ports in order under this breakout mode.
```
{
"interfaces": {
"Ethernet0": {
"index": "1,1,1,1",
"lanes": "0,1,2,3",
"breakout_modes": {
"1x100G[40G]": ["Eth1"],
"2x50G": ["Eth1/1", "Eth1/2"],
"4x25G[10G]": ["Eth1/1", "Eth1/2", "Eth1/3", "Eth1/4"],
"2x25G(2)+1x50G(2)": ["Eth1/1", "Eth1/2", "Eth1/3"],
"1x50G(2)+2x25G(2)": ["Eth1/1", "Eth1/2", "Eth1/3"]
}
}
}
```
#### How to verify it
`config interface breakout`
Signed-off-by: Sangita Maity <samaity@linkedin.com>
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