[CI] Fix deprecations

[smnandre]

Fix multiple deprecations in CI workflows.

doctor-rst.yaml

DOCtor-RST
The `set-output` command is deprecated and will be disabled soon. Please upgrade to using Environment Files. [...]

test.yaml

Note: the failing php-cs-fixer test is unrelated (cause: new rule in php-cs-fixer)
Update: fixed the cs problem, another CI bug appears... not sure if random (does not seem related at all)

JavaScript Coding Style
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/cache@v2. [...]

Check for UnBuilt JS Dist Files
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/cache@v2 [...]

tests-js
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/cache@v2. [...]

test_turbo.yaml

phpstan
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. [...]

tests (8.1, highest)
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. [...]

tests (8.1, lowest)
The following actions uses node12 which is deprecated and will be forced to run on node16: actions/checkout@v2. [...]

[weaverryan]

Thank you a bunch Simon!