Better tooltips and configuration groups

[texodus]

This PR updates Tooltips for the @perspective-dev/viewer-charts package:

• Tooltips use consistent formatting from the Column Settings menu's Format group (see below).
• Tooltips now internally support tables, so labels and values are now aligned properly with conservative overflow, configurable via column_config.
• Tooltips now project intersection target labels against their axes (which also follow the configured Format).
• Tooltip themes work consistently and opacity is also configurable in plugin_config.

Additionally, a new ControlSpec::Group type has been added to plugin_config and columns_config APIs, which allows grouping similar config settings into collapsing panels. Panels can be shift+clicked to expand/collapse all (like in the Datagrid), and the state is persistent within the component. I reserve the option to make "closed" the default in the future if this panel becomes unwieldy, but it is still possible to add top-level components that cannot be hidden (as before).

Drive-bys

• Fixes Int64 handling in Perspective.js #1346
• Fixes a flakey mirror in the C++ cmake dep resolution which was decimating CI.
• Fixed ctrl-C zombify-ing processes in the toolchain.
• Moved ~40 tests which asserted DOM conditions to record tests.
• Fixed default theme bleed from the Light theme.