1.8: hcat does not work with uniform scaling

[PetrKryslUCSD]

With 1.8, Windows 10:

                                                                           
julia> versioninfo()                                                                 
Julia Version 1.8.0-DEV.151                                                          
Commit 6240d352f1 (2021-07-07 19:24 UTC)                                             
Platform Info:                                                                       
  OS: Windows (x86_64-w64-mingw32)                                                   
  CPU: Intel(R) Core(TM) i7-8705G CPU @ 3.10GHz                                      
  WORD_SIZE: 64                                                                      
  LIBM: libopenlibm                                                                  
  LLVM: libLLVM-12.0.0 (ORCJIT, skylake)                                             
Environment:                                                                         
  JULIA_SSL_CA_ROOTS_PATH =       

julia> Hi = rand(3, 3) + 1im*rand(3, 3)                                              
3×3 Matrix{ComplexF64}:                                                              
 0.747577+0.909602im   0.860573+0.995995im   0.323974+0.304666im                     
 0.454257+0.971077im   0.204695+0.0673943im  0.116131+0.517748im                     
 0.231052+0.0728148im  0.277886+0.244845im   0.738274+0.185219im                     
                                                                                     
julia> hcat(Hi, I)                                                                   
ERROR: MethodError: hcat(::Matrix{ComplexF64}, ::UniformScaling{Bool}) is ambiguous. 
Candidates:                                                                          
  hcat(A::Union{Number, UniformScaling, AbstractVecOrMat}...) in LinearAlgebra at C:\Users\PetrKrysl\julia-1.8-dev\share\julia\stdlib\v1.8\LinearAlgebra\src\uniformscaling.jl:409                                                                             
  hcat(As::Union{UniformScaling, LinearMaps.LinearMap, AbstractVecOrMat{T} where T}...) in LinearMaps at C:\Users\PetrKrysl\.julia\packages\LinearMaps\r6i00\src\blockmap.jl:81                                                                                
Possible fix, define                                                                 
  hcat(::Vararg{Union{UniformScaling, AbstractVecOrMat{T} where T}})                 
Stacktrace:                                                                          
 [1] top-level scope                                                                 
   @ REPL[20]:1                                                                      

[PetrKryslUCSD]

Works fine with 1.7.3

[sostock]

This is fixed by #41511.