Instead of passing a single brace pair to FindMatchingBrace(), make it
traverse all brace pairs in buffer.BracePairs on its own.
This has the following advantages:
1. Makes FindMatchingBrace() easier to use, in particular much easier
to use from Lua.
2. Lets FindMatchingBrace() ensure that we use just one matching brace -
the higher-priority one. This fixes the following issues:
([foo]bar)
^
when the cursor is on `[`:
- Both `[]` and `()` pairs are highlighted, whereas the expected
behavior is that only one pair is highlighted - the one that the
JumpToMatchingBrace action would jump to.
- JumpToMatchingBrace action incorrectly jumps to `)` instead of
`]` (which should take higher priority in this case).
In contrast, with `((foo)bar)` it works correctly.
9eb8782ff2