<!--
 Please make sure you've read and understood our contributing guidelines:
 https://github.com/Azure/SONiC/blob/gh-pages/CONTRIBUTING.md

 CODE_OF_CONDUCT.md LICENSE README.md SECURITY.md SUPPORT.md azure-pipelines failure_prs.log scripts skip_prs.log Make sure all your commits include a signature generated with `git commit -s` **

 If this is a bug fix, make sure your description includes "fixes #xxxx", or
 "closes #xxxx" or "resolves #xxxx"

 Please provide the following information:
-->

#### Why I did it
Platform support for 7050SX3 is needed.

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

#### How I did it
Add support for Arista-7050SX3 platforms by introducing/modifying platform directories and bump up `sonic-platform-modules-arista`.

#### How to verify it
Checked with 202511 release and made sure that links come up with these changes.

<!--
If PR needs to be backported, then the PR must be tested against the base branch and the earliest backport release branch and provide tested image version on these two branches. For example, if the PR is requested for master, 202211 and 202012, then the requester needs to provide test results on master and 202012.
-->

#### Which release branch to backport (provide reason below if selected)

<!--
- Note we only backport fixes to a release branch, *not* features!
- Please also provide a reason for the backporting below.
- e.g.
- [x] 202006
-->

- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411
- [ ] 202505
- [x] 202511

#### Tested branch (Please provide the tested image version)

<!--
- Please provide tested image version
- e.g.
- [x] 20201231.100
-->

- [ ] <!-- image version 1 -->
- [ ] <!-- image version 2 -->

#### Description for the changelog
<!--
Write a short (one line) summary that describes the changes in this
pull request for inclusion in the changelog:
-->

<!--
 Ensure to add label/tag for the feature raised. example - PR#2174 under sonic-utilities repo. where, Generic Config and Update feature has been labelled as GCU.
-->

#### Link to config_db schema for YANG module changes
<!--
Provide a link to config_db schema for the table for which YANG model
is defined
Link should point to correct section on https://github.com/Azure/sonic-buildimage/blob/master/src/sonic-yang-models/doc/Configuration.md
-->

Signed-off-by: Sonic Build Admin <sonicbld@microsoft.com>

#### A picture of a cute animal (not mandatory but encouraged)