…c-net#23722)

[Arista-7060X6-64PE-B, Arista-7060X6-16PE-384C-B]: Scale Up NHG

…2412 (#1540)

#### Why I did it
Fix failure to create NHG on TH5 with 512 BGP sessions.

This is a manual cherry-pick to 202412 for original PR:
sonic-net/sonic-buildimage#23722

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

#### How I did it
Set the following fields in the Broadcom configure for the ___ HWSKUs:
`l3_ecmp_member_first_lkup_mem_size: 0`
`l3_ecmp_member_secondary_mem_size: 0`

Also, disable hierarchical nexthop group via sai.profile:
`SAI_NHG_HIERARCHICAL_NEXTHOP=false`

#### How to verify it
Run pre-test checks and confirm they pass.

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

- [ ] 202205
- [ ] 202211
- [ ] 202305
- [ ] 202311
- [ ] 202405
- [ ] 202411
- [x] 202412

#### Tested branch (Please provide the tested image version)
202412

#### Description for the changelog
Scale up NHG, Disable Hierarchical Nexthop

…) (#23779)

[Arista-7060X6-64PE-B, Arista-7060X6-16PE-384C-B]: Scale Up NHG

Why I did it
Fix failure to create NHG on TH5 with 512 BGP sessions.

This is a manual cherry-pick to 202505 for original PR: #23722

Work item tracking
Microsoft ADO (number only):
How I did it
Set the following fields in the Broadcom configure for the ___ HWSKUs:
l3_ecmp_member_first_lkup_mem_size: 0
l3_ecmp_member_secondary_mem_size: 0

Also, disable hierarchical nexthop group via sai.profile:
SAI_NHG_HIERARCHICAL_NEXTHOP=false

How to verify it
Run pre-test checks and confirm they pass.

Which release branch to backport (provide reason below if selected)
 202205
 202211
 202305
 202311
 202405
 202411
 202505
Tested branch (Please provide the tested image version)
202412

Description for the changelog
Scale up NHG, Disable Hierarchical Nexthop

signed-off-by: jianquanye@microsoft.com

Changes missing from msft_202503:
sonic-net/sonic-buildimage#23908
sonic-net/sonic-buildimage#23722

Changes missing from msft_202503:
sonic-net/sonic-buildimage#23908
sonic-net/sonic-buildimage#23722

Was already added for Arista-7060X6-64PE-B-O128 in
#1674

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#### Why I did it

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

#### How I did it

#### How to verify it

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

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- [ ] 201911
- [ ] 202006
- [ ] 202012
- [ ] 202106
- [ ] 202111
- [ ] 202205
- [ ] 202211

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

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…c-net#23722)

[Arista-7060X6-64PE-B, Arista-7060X6-16PE-384C-B]: Scale Up NHG

Signed-off-by: Feng Pan <fenpan@microsoft.com>