Inline code spans reach across block boundaries

codeinline searches the whole remaining source for its closing delimiter. Every other inline rule that can fail to terminate stops at the end of its block.

A stray ` here.

A following paragraph.

! A heading and a `closer` later.

parses as a single <code> holding both following blocks. The heading does not survive.

Non-locality also defeats line-based syntax highlighters, which cannot see whether a closer arrives below the line they are colouring.

$:/core/templates/tiddlywiki5.html and $:/core/templates/tiddlywiki5.js both rely on the reach, so bounding it needs those migrated first.

Pending test on #9920: editions/test/tiddlers/tests/test-wiki-parse-recovery.js, "should stop an inline code span at the end of its block".