run: add -p/--port shortcut to set upload-port and monitor-port simultaneously.

[TinyuZhao]

Description

Problem

When developing with multiple devices connected, specifying --upload-port does not automatically apply to --monitor-port. Users must repeat the same port twice:

pio run -e M5Atom \
  --upload-port /dev/cu.usbserial-6152FEC7E2 \
  --monitor-port /dev/cu.usbserial-6152FEC7E2

Worse, when --upload-port is specified but --monitor-port is not, PlatformIO still scans all available serial ports to find a monitor port. This causes failures when other ports are occupied by different devices:

UserSideException: [Errno 35] Could not exclusively lock port /dev/cu.usbserial-75527D1BB6: 
[Errno 35] Resource temporarily unavailable

This is counterintuitive — the user has already explicitly told PlatformIO which device to use, but PlatformIO still tries to touch other devices.

Expected Behavior

When a user specifies --upload-port, PlatformIO should:

1. Use that port for uploading
2. Default monitor-port to the same port instead of scanning other ports

Solution

Add -p / --port as a shortcut that sets both --upload-port and --monitor-port to the same value:

# Before
pio run -e M5Atom \
  --upload-port /dev/cu.usbserial-6152FEC7E2 \
  --monitor-port /dev/cu.usbserial-6152FEC7E2

# After
pio run -e M5Atom -p /dev/cu.usbserial-6152FEC7E2

Use Case

Multi-device development environment:

Computer
├── /dev/cu.usbserial-AAA  ← Device A (uploading to this one)
├── /dev/cu.usbserial-BBB  ← Device B (occupied by another process)
└── /dev/cu.usbserial-CCC  ← Device C (occupied by another process)

Currently PlatformIO scans and tries to lock all ports even when the target port is explicitly specified, causing unnecessary errors.

[CLAassistant]

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