inspector: process.exit should wait for inspector

[eugeneo]

Checklist

• make -j4 test (UNIX) or vcbuild test nosign (Windows) passes
• the commit message follows commit guidelines

Affected core subsystem(s)

inspector

Description of change

Waits for the inspector frontend to detach when process.exit is called. This enables the user to analyse the profiling information.

Fixes: #7088

[eugeneo]

@ofrobots

[pavelfeldman]

lgtm

[ofrobots]

CI: https://ci.nodejs.org/job/node-test-pull-request/2967/

[bnoordhuis]

LGTM

[bnoordhuis]

For bonus points: factor out that magic number 32 into a constant and update PlatformInit() and WaitForInspectorDisconnect().

[eugeneo]

@bnoordhuis I introduced a constant and rebased the CL

[bnoordhuis]

Can you name it e.g. kNumSignals or kMaxSignal? ALL_CAPS should be reserved for macros. LGTM apart from that.

[eugeneo]

@bnoordhuis I renamed to kMaxSignal. Thanks!

[ofrobots]

New CI: https://ci.nodejs.org/job/node-test-pull-request/2982/

[bnoordhuis]

LGTM. ppcbe-ubuntu1404 seems to be stuck but everything else is green.

[ofrobots]

Thanks, landed as 6626919.

[evanlucas]

I am excluding this one from the next v6.x release since it is just a semver patch release. Once the inspector lands in v6.x, we can remove the dont-land-on-v6.x label. Thanks!