Add auto-generated key methods for Events

[cemozerr]

Description

We want to use typed objects instead of the handwritten events in the codebase so that the event processes are less error-prone, and its easer/ more obvious for users to index these events.

For this purpose, in this PR, we:

• Added an Event trait with methods an event_key(), which returns a given Event object's key, and get_all_event_keys(), which returns all possible event keys for a module, and put this trait as a trait bound on the Event associated type on the Module trait.
• Added an Event macro that derives the Event trait methods for a given enum.
• Renamed the original Event macro that creates an enum that represents all possible events from all the modules to RuntimeEvent.
• Added a get_key_string method to the <runtime>Event enum generated by the (now called) RuntimeEvent macro, which returns a given <Runtime>Event's key.
• Added a get_all_key_strings method to the <runtime>Event enum, which returns the key strings for all events in the runtime, spanning across all modules.
• Renamed the legacy Event type from rollup_interface to LegacyEvent to fix name clashing. The LegacyEvent will be completely removed in an upcoming PR as we move to a simpler Event flow.

The diffs for the macro files are unfortunately bigger than necessary as the name event.rs was more appropriate for the new macro than the previous RuntimeEvent macro.

[codecov[bot]]

Codecov Report

Merging #1116 (c711860) into nightly (5d61e35) will increase coverage by 0.0%. The diff coverage is 91.5%.

Files	Coverage Δ
full-node/db/sov-db/src/ledger_db/mod.rs	90.8% <ø> (ø)
full-node/db/sov-db/src/schema/tables.rs	85.0% <ø> (ø)
full-node/db/sov-db/src/schema/types.rs	80.7% <100.0%> (ø)
full-node/sov-ledger-rpc/src/client.rs	100.0% <ø> (ø)
...ions/integration-tests/src/nested_modules/tests.rs	100.0% <100.0%> (ø)
...ule-system/sov-modules-api/src/state/scratchpad.rs	88.1% <100.0%> (ø)
module-system/sov-modules-macros/src/lib.rs	100.0% <100.0%> (ø)
...ule-system/sov-modules-macros/src/runtime_event.rs	100.0% <100.0%> (ø)
rollup-interface/src/node/rpc/mod.rs	89.2% <ø> (ø)
rollup-interface/src/state_machine/stf.rs	85.7% <ø> (ø)
... and 4 more

... and 1 file with indirect coverage changes

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