Custom SR Linux topology file via binds

[hellt]

Allows a user to bind mount a custom topology file and not conflict with the default topology file.

fix #2506

[codecov]

Codecov Report

Attention: Patch coverage is 76.92308% with 24 lines in your changes missing coverage. Please review.

Project coverage is 52.20%. Comparing base (520d934) to head (bcedfe8).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
nodes/srl/srl.go	74.73%	15 Missing and 9 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2509   +/-   ##
=======================================
  Coverage   52.20%   52.20%           
=======================================
  Files         173      173           
  Lines       17869    17882   +13     
=======================================
+ Hits         9328     9335    +7     
- Misses       7553     7559    +6     
  Partials      988      988           

Files with missing lines	Coverage Δ
utils/containers.go	65.38% <100.00%> (+7.24%)	⬆️
nodes/srl/srl.go	58.34% <74.73%> (+0.30%)	⬆️

... and 1 file with indirect coverage changes

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