Add extraArgs to store spec

[craigfurman]

Q	A
Bug fix?	no
New feature?	yes
API breaks?	no
Deprecations?	no
Related tickets	implements #70, indirectly.
License	Apache 2.0

What's in this PR?

Adds an "extraArgs" field to the store gateway spec, so that users can pass arbitrary flags to thanos-store.

Why?

Additional context

I am not particularly up to date with operator development, and am not sure I've done this the right way. I ran make genall after making my change. This generated some docs. Is this the right sort of thing to do, or are there steps or considerations I've missed?

Checklist

• Code meets the Developer Guide
• User guide and development docs updated (if needed)
• Related Helm chart(s) updated (if needed)

To Do

• If the PR is not complete but you want to discuss the approach, list what remains to be done here

[pepov]

Sorry we haven't been responsing to this so far! I beleive we've added all the missing arguments to the StoreGateway API type and a bit against supporting arbitrary flags, but in case you would still need this, we can consider adding them to all workloads to be consistent.

Feel free to open an issue, I'm closing this.