Add new HWSKU Arista-7060X6-16PE-384C-O128S2-FANOUT so that we can get back to back Paladin ports up with Arista-7060X6-16PE-384C-O128S2 (#22719)

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#### Why I did it

Currently when we loaded HWSKU `Arista-7060X6-16PE-384C-O128S2` on two moby devices and connect their Paladin ports back to back, we can't get link up. It may help if we can get these links up and run the tests.

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it

Created a new `FANOUT` HWSKU containing special lanemap and polarity configs so that we can load `Arista-7060X6-16PE-384C-O128S2` on one Moby and `Arista-7060X6-16PE-384C-O128S2-FANOUT` and get Paladin ports up when connecting them back to back with the following setup:
```
Moby1 Moby2
HWSKU: Arista-7060X6-16PE-384C-O128S2 HWSKU: Arista-7060X6-16PE-384C-O128S2-FANOUT
#17 <-> #18
#19 <-> #20
#21 <-> #22
#23 <-> #24

#18 <-> #17
#20 <-> #19
#22 <-> #21
#24 <-> #23
```

#### How to verify it
Verified that all the Paladin ports can link up with the above setup.

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- [ ] 202305
- [x] msft-202412

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- [x] msft-202412

#### Description for the changelog
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Created `Arista-7060X6-16PE-384C-O128S2-FANOUT` based on `Arista-7060X6-16PE-384C-O128S2` and only update lanemap and polarity settings in bcm config.

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Author: mssonicbld

device/arista/x86_64-arista_7060x6_16pe_384c/Arista-7060X6-16PE-384C-O128S2-FANOUT/buffer_ports.j2

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+../Arista-7060X6-16PE-384C-O128S2/buffer_ports.j2

device/arista/x86_64-arista_7060x6_16pe_384c/Arista-7060X6-16PE-384C-O128S2-FANOUT/buffers.json.j2

@@ -0,0 +1 @@
+../Arista-7060X6-16PE-384C-O128S2/buffers.json.j2

device/arista/x86_64-arista_7060x6_16pe_384c/Arista-7060X6-16PE-384C-O128S2-FANOUT/buffers_defaults_t0.j2

@@ -0,0 +1 @@
+../Arista-7060X6-16PE-384C-O128S2/buffers_defaults_t0.j2

device/arista/x86_64-arista_7060x6_16pe_384c/Arista-7060X6-16PE-384C-O128S2-FANOUT/buffers_defaults_t1.j2

@@ -0,0 +1 @@
+../Arista-7060X6-16PE-384C-O128S2/buffers_defaults_t1.j2