Update flux build to have parity with other flux commands

[allenporter]

This is a breaking change that updates the format of the flux build command to have parity with get and diff commands.

Example to build a single kustomziation:

$ flux-local build ks apps --path tests/testdata/cluster/

Example to inflate a single helm release:

$ flux-local build hr podinfo -n podinfo --path tests/testdata/cluster

The old behavior flux-local build tests/testdata/cluster/ can still be achieved with build all:

$ flux-local build all tests/testdata/cluster/

Fixes #795

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.40%. Comparing base (e59d232) to head (c08e376).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #798      +/-   ##
==========================================
+ Coverage   93.22%   93.40%   +0.17%     
==========================================
  Files          20       20              
  Lines        2229     2288      +59     
==========================================
+ Hits         2078     2137      +59     
  Misses        151      151              

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