Cleanup executor resources after execution

[martinRenou]

Exploring solutions for #896

[martinRenou]

Please don't merge yet, just trying the CI

[github-actions]

Benchmark report

The execution time (in milliseconds) are grouped by test file, test type and browser.
For each case, the following values are computed: min <- [1st quartile - median - 3rd quartile] -> max.

Results table

Test file	basics.ipynb	bqplot.ipynb	dashboard.ipynb	gridspecLayout.ipynb	interactive.ipynb	ipympl.ipynb	ipyvolume.ipynb	multiple_widgets.ipynb	query-strings.ipynb
Render
chromium
actual	3469 <- [3510 - 3559 - 3840] -> 4397	3282 <- [3371 - 3471 - 3477] -> 3668	3368 <- [3644 - 3660 - 3674] -> 3717	4626 <- [4710 - 4743 - 4751] -> 4790	2443 <- [2512 - 2521 - 2571] -> 2765	3471 <- [3474 - 3498 - 3622] -> 3766	17222 <- [17425 - 19835 - 20799] -> 21609	14988 <- [15094 - 15121 - 15192] -> 15392	1445 <- [1676 - 1815 - 1908] -> 1924
expected	3379 <- [3442 - 3517 - 3701] -> 3876	2976 <- [3227 - 3321 - 3421] -> 3604	3608 <- [3623 - 3709 - 3793] -> 3825	4453 <- [4453 - 4523 - 4661] -> 4748	2559 <- [2655 - 2656 - 2660] -> 2674	3982 <- [4079 - 4213 - 4356] -> 4743	12183 <- [18509 - 19553 - 20811] -> 21515	15319 <- [15660 - 15796 - 15912] -> 16056	1517 <- [1920 - 1997 - 2103] -> 2113

❗ Test metadata have changed

--- /dev/fd/63	2021-09-17 08:10:37.276982177 +0000
+++ /dev/fd/62	2021-09-17 08:10:37.276982177 +0000
@@ -8,27 +8,27 @@
   },
   "systemInformation": {
     "cpu": {
-      "brand": "Xeon® E5-2673 v4",
+      "brand": "Xeon® E5-2673 v3",
       "cache": {
         "l1d": 65536,
         "l1i": 65536,
         "l2": 524288,
-        "l3": 52428800
+        "l3": 31457280
       },
       "cores": 2,
       "family": "6",
-      "flags": "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm 3dnowprefetch invpcid_single pti fsgsbase bmi1 hle avx2 smep bmi2 erms invpcid rtm rdseed adx smap xsaveopt md_clear",
+      "flags": "fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx pdpe1gb rdtscp lm constant_tsc rep_good nopl xtopology cpuid pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 movbe popcnt aes xsave avx f16c rdrand hypervisor lahf_lm abm invpcid_single pti fsgsbase bmi1 avx2 smep bmi2 erms invpcid xsaveopt md_clear",
       "governor": "",
       "manufacturer": "Intel®",
-      "model": "79",
+      "model": "63",
       "physicalCores": 2,
       "processors": 1,
       "revision": "",
       "socket": "",
-      "speed": 2.3,
+      "speed": 2.4,
       "speedMax": null,
       "speedMin": null,
-      "stepping": "1",
+      "stepping": "2",
       "vendor": "GenuineIntel",
       "virtualization": false,
       "voltage": ""
@@ -42,11 +42,11 @@
       "codename": "Focal Fossa",
       "codepage": "UTF-8",
       "distro": "Ubuntu",
-      "kernel": "5.8.0-1041-azure",
+      "kernel": "5.8.0-1040-azure",
       "logofile": "ubuntu",
       "platform": "linux",
       "release": "20.04.3 LTS",
-      "serial": "faac5b9e00cf4ae3b2d2c013e98d933a",
+      "serial": "cfc067bfcb844f35865e279a1b0e66c5",
       "servicepack": "",
       "uefi": false
     }

[jtpio]

Thanks!