Combined -Wextra -Werror Commits

[aws-nslick]

CI is moving too slowly, and rebasing triggers too many rebuilds, to continue to use stacked PRs. This is a single PR that is combining all of the following PRS:

• b45d7e8 (feat(build): add -Wextra to "picky" compiler flags #588) (approved, marked as merged)
• 0780149 (fix(build): check features before mangling CFLAGS #589) (initially unapproved, changes made as requested, approved and marked as merged)
• 247e96a (fix(platform-aws): fill all platform values #595) (approved, marked as merged)
• f50eecd (fix(tracing/nvtx): silence -Wmissing-field-initializer warnings #593) (approved, marked as merged)
• 2b2e91e (fix(test): fix typing issues #587) (approved, marked as merged)
• 441e1e8 (fix(neuron): remove const from ncclNetPlugin_v{4,5} syms #577) (approved, marked as merged)
• 1040fef (fix(sendrecv): add missing nccl-headers include #576) (approved, marked as merged)
• 5faa97d (fix(rdma): avoid enum/integral comparison #586) (approved, marked as merged)
• 1ecfffb (fix(rdma): use COMM_ID_MASK as invalid id #574) (approved, marked as merged)
• 8cb419b (feat(param): add uint parameter macro #570) (approved, marked as merged)
• ab14b17 (fix(tuner): fix implicit conversions #573) (approved, marked as merged)
• e067641 (fix(tuner): avoid gotos #569) (approved, marked as merged)
• 4a2d0b1 (fix(tree): add fallthrough switch markers #585) (approved, marked as merged)
• 13a67d1 (fix(tree): avoid sign comparison issues #575) (initially unapproved, changes made as requested, approved and marked as merged)
• 24c9d4b (fix(tree): use decltype instead of typeof for cxx #565) (approved and marked as merged)
• 30efcbf (fix(tree): move declarations to top of function #563) ( ❌ needs reapproval, will automatically be marked as merged by the landing of this PR)

For and PR marked above as unapproved, please click and re-review it. It will land (but will not be targeting master). Once all commits are "merged" into a some non-master branch, then we can just approve this PR, containing roughly the same contents, and we can merge it to master all-together and delete the branches.

I would prefer to be able to just land directly into master by changing base branches, but it's not realistic today given the way that CI is triggering. So here we are.

Description of changes:

Bunch of changes that bring us significantly closer to building successfully with C++, but also enables -Werror -Wextra going forward, and CI actions ensure that it will stay that way. I'm not sure that this is all pointless and nit-picky, a build failure caught on #624 very possibly can explain a segfault that was reported when initializing the plugin when less than 32 EFAs are available.

edit: needed to be rebased due to a bug introduced during rebase on the very first in the series, see comment here.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[aws-nslick]

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[aws-nslick]

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