Add full bril-rs feature set to rs2bril

[ajpal]

Similar to #312, this PR adds the full feature set to rs2bril so that we can depend on both.

[Pat-Lafon]

Two quick questions:

• what happens if you don't include some features that rs2bril will never use/consider like ssa, speculate?
• Instead of adding some features as default and continuing feature creep spread. Can we just enable them as feature flags like import? (Ideally most of the rust tools should do this though when I explored this, lalrpop had an open missing feature I would have needed.)

[ajpal]

• what happens if you don't include some features that rs2bril will never use/consider like ssa, speculate?
  I think this works! I updated to only add import

• Instead of adding some features as default and continuing feature creep spread. Can we just enable them as feature flags like import? (Ideally most of the rust tools should do this though when I explored this, lalrpop had an open missing feature I would have needed.)
  Sorry, I'm not really sure what that means / how to do it? If the import feature is enabled, that changes the fields that need to be included in the Program struct. Is there a way to do that other than making import always enabled for rs2bril?

[Pat-Lafon]

Sorry, I'm not really sure what that means / how to do it? If the import feature is enabled, that changes the fields that need to be included in the Program struct. Is there a way to do that other than making import always enabled for rs2bril?

Something like

bril/brilirs/Cargo.toml

Lines 46 to 47 in 0eedeea

	[features]
	completions = ["clap_complete"]

but instead of enabling an optional dependency, enable the bril-rs feature flag for import and then feature gate that one change that import requires for the Program struct

[sampsyo]

@Pat-Lafon's useful comments aside, it looks like cargo fmt is suggesting a minuscule change here!

[sampsyo]

Thanks, @ajpal! @Pat-Lafon, if this looks good to you now, I'm down to merge.

[Pat-Lafon]

LGTM

[ajpal]

@sampsyo @Pat-Lafon Is this ready to merge then? Lmk if there are any other changes you'd like me to make!

[Pat-Lafon]

@sampsyo @Pat-Lafon Is this ready to merge then? Lmk if there are any other changes you'd like me to make!

It should be good, just probably low on Adrian's busy queue.

[sampsyo]

I was on vacation this week. 😃 Looks good though; thank you again!