This flag was added to evaluate performance relative to tokio's threaded
runtime. Although it's faster in the HTTP benchmark, it's clear the runtime
is not the only perf problem.
Removing this flag will simplify further refactors, in particular
adopting the #[tokio::main] macro. This will be done in a follow up.
Ultimately we expect to move to the current thread runtime with Isolates
pinned to specific threads, but that will be a much larger refactor. The
--current-thread just complicates that effort.
Before:
```
▶ target/debug/deno https://deno.land/std/examples/echo_server.ts
error: Uncaught PermissionDenied: run again with the --allow-net flag
► $deno$/dispatch_json.ts:40:11
at DenoError ($deno$/errors.ts:20:5)
at unwrapResponse ($deno$/dispatch_json.ts:40:11)
at sendSync ($deno$/dispatch_json.ts:67:10)
at listen ($deno$/net.ts:170:15)
at https://deno.land/std/examples/echo_server.ts:4:23
```
```
▶ target/debug/deno --allow-read=/usr https://deno.land/std/examples/cat.ts /etc/passwd
error: Uncaught PermissionDenied: run again with the --allow-read flag
► $deno$/dispatch_json.ts:40:11
at DenoError ($deno$/errors.ts:20:5)
at unwrapResponse ($deno$/dispatch_json.ts:40:11)
at sendAsync ($deno$/dispatch_json.ts:91:10)
```
After:
```
▶ target/debug/deno https://deno.land/std/examples/echo_server.ts
error: Uncaught PermissionDenied: network access to "0.0.0.0:8080", run again with the --allow-net flag
► $deno$/dispatch_json.ts:40:11
at DenoError ($deno$/errors.ts:20:5)
at unwrapResponse ($deno$/dispatch_json.ts:40:11)
at sendSync ($deno$/dispatch_json.ts:67:10)
at listen ($deno$/net.ts:170:15)
at https://deno.land/std/examples/echo_server.ts:4:23
```
```
▶ target/debug/deno --allow-read=/usr https://deno.land/std/examples/cat.ts /etc/passwd
error: Uncaught PermissionDenied: read access to "/etc/passwd", run again with the --allow-read flag
► $deno$/dispatch_json.ts:40:11
at DenoError ($deno$/errors.ts:20:5)
at unwrapResponse ($deno$/dispatch_json.ts:40:11)
at sendAsync ($deno$/dispatch_json.ts:91:10)
```
