Add support for customUserData with Bottlerocket

[suket22]

1. Issue, if available:
N/A

2. Description of changes:
This change only adds support for customUserData with Bottlerocket AMIFamily. It follows what's defined in this doc for the most part. The one main change is that I'm no longer merging labels / taints from the custom userData but rather overwriting them completely. This is because of what we discovered here regarding kubelet not merging in other labels. As long as Karpenter creates the node object itself, there's no point merging in labels / taints etc.

3. How was this change tested?

• I've tested this locally - ran through both the provider level validation checks.
• The bootstrap logic isn't unit tested but I've been testing it out locally and my nodes are joining the cluster. I haven't tried the full extent of all BR settings but most that I've tried have worked.

4. Does this change impact docs?

• Yes, PR includes docs updates
• Yes, issue opened: link to issue
• No

I'm thinking of only adding docs once AL2 support is here.

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

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[tzneal]

I haven't tested this, but the changes LGTM

[bwagner5]

can you add docs with an example of a simple bottlerocket config in the provisioner?

And can you add a test too?

[suket22]

can you add docs with an example of a simple bottlerocket config in the provisioner?

And can you add a test too?

I intentionally left the docs out. I was thinking of adding them once I've got support for both AMI families rather than just one, but can add them now.

I'll add a few tests 👍

[bwagner5]

Just a few doc nits, but otherwise lgtm!

[bwagner5]

nice!

Docs and tests were added.