Update context output format to reduce duplication

[rfbgo]

This is a breaking change for anyone who consumes our output format wrt contexts

This PR makes it so that contexts only use the format string when printing, to reduce how repetitive and annoying to construct the format is.

The new output looks like:

txt

 10   Bytes: 0 (BW) figures of merit:
 11     Bandwidth = 0.00 Mbytes/sec

json

131         {
132           "name": "Bytes: 0 (BW)",
133           "foms": [
134             {
135               "value": "0.00",
136               "units": "Mbytes/sec",
137               "origin": "IntelMpiBenchmarks",
138               "origin_type": "application",
139               "name": "Bandwidth"
140             }
141           ]
142         },

This is also reflected the same way in the upload db

The old formats looked like:

txt

 10   Bytes: bytes (BW) = Bytes: 0 (BW) figures of merit:
 11     Bandwidth = 0.00 Mbytes/sec

json

  "name": "Bytes: bytes (BW) = Bytes: 0 (BW)",
133           "foms": [
134             {
135               "value": "0.00",
136               "units": "Mbytes/sec",
137               "origin": "IntelMpiBenchmarks",
138               "origin_type": "application",
139               "name": "Bandwidth"
140             }
141           ]
142         },

[douglasjacobsen]

Looks good, once the CI passes