Add Voila app port to kernel env

[dcnadler]

Similar to #1141, which added VOILA_SERVER_URL to the kernel env, this adds VOILA_APP_PORT.

The purpose is to make using preheated kernels with wait_for_request() easier when not using the default port.

[github-actions]

👈 Launch a Binder on branch dcnadler/voila/app_port_to_env

[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	voila-tree-classic.ipynb	voila-tree-light.ipynb	voila-tree-dark.ipynb	voila-tree-miami.ipynb	basics.ipynb	bqplot.ipynb	dashboard.ipynb	gridspecLayout.ipynb	interactive.ipynb	ipympl.ipynb	ipyvolume.ipynb	multiple_widgets.ipynb	query-strings.ipynb	reveal.ipynb
Render
chromium
actual	233 <- [278 - 358 - 505] -> 959	92 <- [101 - 116 - 149] -> 245	76 <- [79 - 87 - 102] -> 151	67 <- [74 - 82 - 99] -> 125	2363 <- [2404 - 2440 - 2540] -> 3361	2188 <- [2224 - 2234 - 2289] -> 2620	2456 <- [2483 - 2625 - 2685] -> 2984	2386 <- [2398 - 2435 - 2599] -> 2839	1704 <- [1705 - 1722 - 1819] -> 2002	3305 <- [3337 - 3448 - 3752] -> 4411	7516 <- [8603 - 8818 - 9687] -> 9730	6045 <- [6084 - 6178 - 6191] -> 6310	1216 <- [1317 - 1339 - 1390] -> 1436	2319 <- [2369 - 2384 - 2422] -> 2628
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	2022-07-25 23:26:59.702729094 +0000
+++ /dev/fd/62	2022-07-25 23:26:59.702729094 +0000
@@ -4,37 +4,37 @@
     "BENCHMARK_REFERENCE": "actual"
   },
   "browsers": {
-    "chromium": "97.0.4666.0"
+    "chromium": "94.0.4595.0"
   },
   "systemInformation": {
     "cpu": {
-      "brand": "Xeon® Platinum 8370C",
+      "brand": "Xeon® E5-2673 v3",
       "cache": {
-        "l1d": 98304,
+        "l1d": 65536,
         "l1i": 65536,
-        "l2": 2097152,
-        "l3": 50331648
+        "l2": 524288,
+        "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 avx512f avx512dq rdseed adx smap clflushopt avx512cd avx512bw avx512vl xsaveopt xsavec xsaves 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": "106",
+      "model": "63",
       "physicalCores": 2,
       "processors": 1,
       "revision": "",
       "socket": "",
-      "speed": 2.8,
+      "speed": 2.4,
       "speedMax": null,
       "speedMin": null,
-      "stepping": "6",
+      "stepping": "2",
       "vendor": "GenuineIntel",
       "virtualization": false,
       "voltage": ""
     },
     "mem": {
-      "total": 7281008640
+      "total": 7291699200
     },
     "osInfo": {
       "arch": "x64",
@@ -42,11 +42,11 @@
       "codename": "Focal Fossa",
       "codepage": "UTF-8",
       "distro": "Ubuntu",
-      "kernel": "5.15.0-1014-azure",
+      "kernel": "5.8.0-1040-azure",
       "logofile": "ubuntu",
       "platform": "linux",
-      "release": "20.04.4 LTS",
-      "serial": "2dc2d73cec5c409b97a391e53a41a4ba",
+      "release": "20.04.3 LTS",
+      "serial": "cfc067bfcb844f35865e279a1b0e66c5",
       "servicepack": "",
       "uefi": false
     }

[dcnadler]

Thanks for clarifying @trungleduc! I updated the code

[trungleduc]

Thanks!