[rts] [WIP] [RFC] Add all information from '+RTS -s' to '+RTS -t --machine-readable'wip/better-machine-readable-stats

Summary:
This is a rough draft to see if this is likely to be mergable.

Example of the new output:
```
 ["bytes_allocated", "13563288")
 ,"num_GCs", "13")
 ,"average_bytes_used", "461388")
 ,"num_byte_usage_samples", "673072")
 ,"num_byte_usage_samples", "2")
 ,"peak_megabytes_allocated", "7")
 ,"init_cpu_seconds", "0.002")
 ,"init_wall_seconds", "0.001")
 ,"mut_cpu_seconds", "0.007")
 ,"mut_wall_seconds", "0.006")
 ,"GC_cpu_seconds", "0.046")
 ,"GC_wall_seconds", "0.012")
 ,"copied_bytes", "2482464")
 ,"max_slop_bytes", "84688")
 ,"fragmentation_megabytes", "0")
 ,"gc-0-collections", "11")
 ,"gc-0-par_collections", "11")
 ,"gc-0-cpu_time_seconds", "0.00856")
 ,"gc-0-wall_time_seconds", "0.00214")
 ,"gc-0-avg_pause", "0.00019")
 ,"gc-0-max_pause", "0.00047")
 ,"gc-1-collections", "2")
 ,"gc-1-par_collections", "1")
 ,"gc-1-cpu_time_seconds", "0.03787")
 ,"gc-1-wall_time_seconds", "0.00999")
 ,"gc-1-avg_pause", "0.00499")
 ,"gc-1-max_pause", "0.00929")
 ,"work_balance", "7.78722")
 ,"task_count", "10")
 ,"bound_tasks_count", "1")
 ,"peak_worker_count", "9")
 ,"worker_count", "9")
 ,"n_capabilities", "4")
 ,"sparks_count", "0")
 ,"sparks_converted", "0")
 ,"sparks_overflowed", "0")
 ,"sparks_dud", "0")
 ,"sparks_garbage_collected", "0")
 ,"sparks_fizzled", "0")
 ,"alloc_rate", "1821930646")
 ,"productivity_user_percent", "14.26508")
 ,"productivity_elapsed_percent", "36.28410")
 ,"gc_alloc_block_sync.spin", "55")
 ,"gc_alloc_block_sync.yield", "0")
 ,"whitehole_gc.spin", "0")
 ,"whitehole_gc.yield", "0")
 ,"whitehole_lock_closure_spin", "0")
 ,"whitehole_lock_closure_yield", "0")
 ,"waitForGcThreads_spin", "123")
 ,"waitForGcThreads_yield", "1270")
 ,"gc_sync-0-spin", "0")
 ,"gc_sync-0-yield", "0")
 ,"gc_sync-1-spin", "1")
 ,"gc_sync-1-yield", "0")
 ]
 ```
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Reviewers: bgamari, erikd, simonmar

Subscribers: rwbarton, thomie, carter

Differential Revision: https://phabricator.haskell.org/D4303

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