Backports for 0.27.22

[mortenpi]

X-refs: #1886

[mortenpi]

@fredrikekre Are the 1.0 failures a Pkg resolver bug..? It should be possible to install

Documenter 0.27.22
DocStringExtensions 0.8.6
DocumenterTools 0.1.12

together. From the CI logs:

ERROR: Unsatisfiable requirements detected for package DocumenterTools [35a29f4d]:
 DocumenterTools [35a29f4d] log:
 ├─possible versions are: 0.1.0-0.1.14 or uninstalled
 ├─restricted to versions * by an explicit requirement, leaving only versions 0.1.0-0.1.14
 └─restricted by compatibility requirements with DocStringExtensions [ffbed154] to versions: uninstalled — no versions left
   └─DocStringExtensions [ffbed154] log:
     ├─possible versions are: [0.4.6, 0.5.0, 0.6.0, 0.7.0, 0.8.0-0.8.6, 0.9.0] or uninstalled
     ├─restricted to versions [0.4.0-0.4, 0.5.0-0.5, 0.6.0-0.6, 0.7.0-0.7, 0.8.0-0.8, 0.9.0-0.9] by Documenter [e30172f5], leaving only versions [0.4.6, 0.5.0, 0.6.0, 0.7.0, 0.8.0-0.8.6, 0.9.0]
     │ └─Documenter [e30172f5] log:
     │   ├─possible versions are: 0.27.22 or uninstalled
     │   └─Documenter [e30172f5] is fixed to version 0.27.22
     └─restricted to versions 0.9.0 by an explicit requirement, leaving only versions 0.9.0
Stacktrace:
 [1] #propagate_constraints!#61(::Bool, ::Function, ::Pkg.GraphType.Graph, ::Set{Int64}) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/GraphType.jl:1007
 [2] propagate_constraints! at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.0/Pkg/src/GraphType.jl:9[48](https://github.com/JuliaDocs/Documenter.jl/runs/7477958570?check_suite_focus=true#step:6:51) [inlined]

It seems I can also replicate this locally, when I try to add DocumenterTools to the environment. It looks like it doesn't want to downgrade DocStringExtensions.

[fredrikekre]

This happens because Documenters env is instantiated first, installing DocStringExtensions 0.9. This becomes a hard requirement, so when resolving the test env there is no version of DocumenterTools that support this. Easiest fix is JuliaDocs/DocumenterTools.jl#63 to relase a version with JuliaDocs/DocumenterTools.jl@bfacbbf included.

[mortenpi]

Nice, cheers @fredrikekre!