[Bootstrap Agent] Provide configuration option to distinguish between "scrimlet / gimlet"

[smklein]

... this influences the decision of whether or not to launch RSS.

• Track local hardware information to make this decision locally within the sled: [sled-agent] Monitor for Tofino driver as factor in 'are we scrimlet' decision #1918
• Use this information as a factor in "whether or not to launch RSS"
• Use this information as a factor in "whether or not to launch the switch zone": done in [sled-agent] Launch switch zone automatically on scrimlets #1933
• Report the "is gimlet/scrimlet" info upward to Nexus #1511

[smklein]

Well, one workaround to consider: We currently decide whether or not to launch RSS by the presence / absence of a "config-rss.toml" file. For now, that has been a sufficient signal - launching RSS has been the only action we'd conditionally take - but it would still be worth making this explicit.