feat(vpc-gw): add support for SSH bastion

[remyleone]

Waiting on the VPC team to add support for bastion related fields in the create request

[codecov-commenter]

Codecov Report

Merging #1255 (239bc73) into master (4215bc3) will increase coverage by 0.02%.
The diff coverage is 74.41%.

@@            Coverage Diff             @@
##           master    #1255      +/-   ##
==========================================
+ Coverage   69.88%   69.91%   +0.02%     
==========================================
  Files         102      102              
  Lines       16309    16330      +21     
==========================================
+ Hits        11398    11417      +19     
  Misses       3929     3929              
- Partials      982      984       +2     

Impacted Files	Coverage Δ
scaleway/helpers_rdb.go	82.66% <ø> (+3.29%)	⬆️
scaleway/helpers.go	75.19% <40.00%> (-0.47%)	⬇️
scaleway/resource_vpc_public_gateway.go	74.46% <78.37%> (+0.39%)	⬆️
scaleway/resource_rdb_instance.go	71.33% <100.00%> (ø)

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