[kernel] Deprecates Db.Main

src/kernel_internals/runtime/boot.ml

src/kernel_internals/runtime/boot.mli

src/kernel_services/plugin_entry_points/db.ml

src/kernel_services/plugin_entry_points/db.mli

src/plugins/alias/Alias.ml

src/plugins/aorai/aorai_register.ml

src/plugins/api-generator/api_generator.ml

src/plugins/callgraph/register.ml

src/plugins/constant_propagation/api.ml

src/plugins/dive/main.ml

src/plugins/e-acsl/examples/demo/script.ml

src/plugins/e-acsl/src/main.ml

src/plugins/eva/engine/analysis.ml

src/plugins/from/from_register.ml

src/plugins/gui/menu_manager.ml

src/plugins/impact/register.ml

src/plugins/inout/register.ml

src/plugins/loop_analysis/register.ml

src/plugins/markdown-report/mdr_register.ml

src/plugins/metrics/register.ml