fix(remote-build): parse --launchpad-timeout argument

[mr-cal]

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Two changes:

1. Fix a regression where --launchpad-timeout was not parsed and could not be used by the fallback remote builder.
2. Add support for --launchpad-timeout in new remote builder

Note - I made 2 PRs (this one and #4427) because the remote build code is very different between main and the hotfix/7.5 branches (main has the new remote builder code, hotfix/7.5 does not).

Fixes #4397
(CRAFT-2094)

[codecov-commenter]

Codecov Report

Merging #4426 (ea85f98) into main (e3b8a3a) will increase coverage by 0.02%.
The diff coverage is 100.00%.

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@@            Coverage Diff             @@
##             main    #4426      +/-   ##
==========================================
+ Coverage   89.18%   89.20%   +0.02%     
==========================================
  Files         322      322              
  Lines       21659    21663       +4     
==========================================
+ Hits        19316    19324       +8     
+ Misses       2343     2339       -4     

Files	Coverage Δ
snapcraft/commands/remote.py	98.78% <100.00%> (+<0.01%)	⬆️
snapcraft/remote/errors.py	100.00% <100.00%> (ø)
snapcraft/remote/launchpad.py	89.06% <100.00%> (+1.66%)	⬆️
snapcraft/remote/remote_builder.py	100.00% <100.00%> (ø)

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[mr-cal]

Store spread test failure is unrelated (#4411)