Use availableParallelism, handle empty os.cpus()

When /proc is not available and os.cpus() returns an empty list,
callLimit() doesn't run any of the functions. Fix this and also update
tap which was broken in newer node versions

PR-URL: isaacs#11
Credit: @codedokode
Close: isaacs#11
Reviewed-by: @isaacs

index.js

@@ -1,4 +1,7 @@
-const defLimit = require('os').cpus().length
+const os = require('os')
+// availableParallelism available only since node v19, for older versions use cpus()
+// cpus() can return an empty list if /proc is not mounted, use 1 in this case
+const defLimit = 'availableParallelism' in os ? os.availableParallelism() : Math.max(1, os.cpus().length)
 const callLimit = (queue, limit = defLimit) => new Promise((res, rej) => {
   let active = 0
   let current = 0