rapid-metrics: Use fsnotifywatch to gather filesystem statistics

[badboy]

Uses fsnotifywatch for some statistics to compare rkv/sqlite and delay-ping-lifetime-io

Output like:

    Finished `release` profile [optimized + debuginfo] target(s) in 0.06s
===== Full write mode (Rkv) =====
target/release/rapid-metrics --maxn 10000 --seed 100 /tmp/glean_rapid_metrics.l6IRqgKAnC
Establishing watches...
Finished establishing watches, now collecting statistics.
total  modify  close_write  open  moved_from  moved_to  create  delete  filename
102333  25588   25588        25588  25585       0         25585   0       /tmp/glean_rapid_metrics.l6IRqgKAnC/db/data.safe.tmp (deleted)
25585  0       0            0     0           25585     0       0       /tmp/glean_rapid_metrics.l6IRqgKAnC/db/data.safe.bin
1      0       0            0     0           0         1       0       /tmp/glean_rapid_metrics.l6IRqgKAnC/pending_pings
1      0       0            0     0           0         1       0       /tmp/glean_rapid_metrics.l6IRqgKAnC/tmp
1      0       0            0     0           0         0       1       /tmp/glean_rapid_metrics.l6IRqgKAnC/pending_pings/66ecdac9-ad85-4384-af16-87e17173dd92 (deleted)

===== delay-ping-lifetime mode (Rkv) =====
target/release/rapid-metrics --maxn 10000 --seed 100 /tmp/glean_rapid_metrics.P08YlTv9ea --delay
Establishing watches...
Finished establishing watches, now collecting statistics.
total  modify  close_write  open  moved_from  moved_to  create  delete  filename
22991  5753    5753         5753  5753        0         5753    0       /tmp/glean_rapid_metrics.P08YlTv9ea/db/data.safe.tmp
5753   0       0            0     0           5753      0       0       /tmp/glean_rapid_metrics.P08YlTv9ea/db/data.safe.bin
1      0       0            0     0           0         1       0       /tmp/glean_rapid_metrics.P08YlTv9ea/pending_pings
1      0       0            0     0           0         1       0       /tmp/glean_rapid_metrics.P08YlTv9ea/tmp
1      0       0            0     0           0         0       1       /tmp/glean_rapid_metrics.P08YlTv9ea/pending_pings/949b6af2-16ff-4501-b0f3-7196c7efde23 (deleted)

    Finished `release` profile [optimized + debuginfo] target(s) in 0.06s
===== Full write mode (SQLite) =====
target/release/rapid-metrics --maxn 10000 --seed 100 /tmp/glean_rapid_metrics.UbKKXVgtPn
Establishing watches...
Finished establishing watches, now collecting statistics.
total  access  modify  close_write  close_nowrite  open  create  delete  filename
24330  177     24149   1            0              1     1       1       /tmp/glean_rapid_metrics.UbKKXVgtPn/db/glean.sqlite-wal
218    2       216     1            0              0     0       0       /tmp/glean_rapid_metrics.UbKKXVgtPn/db/glean.sqlite
5      0       2       1            0              1     1       1       /tmp/glean_rapid_metrics.UbKKXVgtPn/db/glean.sqlite-shm
3      0       1       1            0              1     1       0       /tmp/glean_rapid_metrics.UbKKXVgtPn/client_id.txt
2      0       0       1            0              0     0       1       /tmp/glean_rapid_metrics.UbKKXVgtPn/db/glean.sqlite-journal (deleted)
2      0       0       0            1              0     0       1       /tmp/glean_rapid_metrics.UbKKXVgtPn/pending_pings/37943311-b5a1-40f1-9e96-6336ddf36b09
1      0       0       0            0              0     1       0       /tmp/glean_rapid_metrics.UbKKXVgtPn/pending_pings
1      0       0       0            0              0     1       0       /tmp/glean_rapid_metrics.UbKKXVgtPn/tmp

===== delay-ping-lifetime mode (SQLite) =====
target/release/rapid-metrics --maxn 10000 --seed 100 /tmp/glean_rapid_metrics.jg6AsTmXrP --delay
Establishing watches...
Finished establishing watches, now collecting statistics.
total  access  modify  close_write  open  create  delete  filename
11243  83      11156   1            1     1       1       /tmp/glean_rapid_metrics.jg6AsTmXrP/db/glean.sqlite-wal
97     2       95      1            0     0       0       /tmp/glean_rapid_metrics.jg6AsTmXrP/db/glean.sqlite
8      0       5       1            1     1       1       /tmp/glean_rapid_metrics.jg6AsTmXrP/db/glean.sqlite-shm
3      0       1       1            1     1       0       /tmp/glean_rapid_metrics.jg6AsTmXrP/client_id.txt
2      0       1       1            0     0       1       /tmp/glean_rapid_metrics.jg6AsTmXrP/db/glean.sqlite-journal (deleted)
1      0       0       0            0     1       0       /tmp/glean_rapid_metrics.jg6AsTmXrP/pending_pings
1      0       0       0            0     1       0       /tmp/glean_rapid_metrics.jg6AsTmXrP/tmp
1      0       0       0            0     0       1       /tmp/glean_rapid_metrics.jg6AsTmXrP/pending_pings/630d5fe7-3623-4286-b70a-d381e6d140a7 (deleted)

Linux only.

[badboy]

The script could use some work to make it easier to compare. But regardless I think this is worth landing already, for the rapid-metrics changes alone (I'm using them locally to test out things already)