chore(api,robot-server): update testing dev deps

[mcous]

Overview

This PR is 1 of 4 that are working towards #7816.

1. chore(api,robot-server): update testing dev deps chore(api,robot-server): update testing dev deps #7855
2. refactor(robot-server): add experimental protocol router refactor(robot-server): add experimental protocol router #7856
3. refactor(api): add create_file_runner factory refactor(api): add create_file_runner factory #7857
4. refactor(robot-server): start wiring /sessions into runner and engine refactor(robot-server): start wiring /sessions into runner and engine #7858

This PR makes three changes to the api's and robot-server's dev-dep list. Pulled out into its own PR to keep imminent PR's more manageable.

Changelog

• Swaps out pytest-watch for the much more active pytest-xdist
  • Can now do watch mode with pipenv run pytest <files> --looponfail --color=yes
• Adds httpx to use as a test client in async FastAPI router tests
• Upgrades decoy for a few new matchers and a typing fix to stop mypy complaining if you pass an ABC to the spec argument

Review requests

• Test and lint dev tasks in api and robot-server still run locally on your machine
• pytest ... --looponfail --color=yes watch mode works on your machine

Risk assessment

Only risk should be to our dev environment

[codecov]

Codecov Report

Merging #7855 (c4060fe) into edge (5f9c15d) will decrease coverage by 9.96%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             edge    #7855      +/-   ##
==========================================
- Coverage   93.51%   83.54%   -9.97%     
==========================================
  Files         124      344     +220     
  Lines        4921    21494   +16573     
==========================================
+ Hits         4602    17958   +13356     
- Misses        319     3536    +3217     

Impacted Files	Coverage Δ
opentrons/calibration_storage/types.py	100.00% <0.00%> (ø)
opentrons/hardware_control/modules/update.py	28.12% <0.00%> (ø)
opentrons/hardware_control/__main__.py	0.00% <0.00%> (ø)
opentrons/commands/helpers.py	86.36% <0.00%> (ø)
opentrons/config/pipette_config.py	94.05% <0.00%> (ø)
...protocols/context/protocol_api/protocol_context.py	90.84% <0.00%> (ø)
opentrons/hardware_control/adapters.py	84.84% <0.00%> (ø)
opentrons/commands/protocol_commands.py	94.73% <0.00%> (ø)
opentrons/hardware_control/emulation/util.py	84.21% <0.00%> (ø)
opentrons/protocol_engine/protocol_engine.py	97.50% <0.00%> (ø)
... and 210 more

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[SyntaxColoring]

LGTM.