[4/7] refactor(core): re-export formatting symbols from `cursive_core`

[arxanas]

Stack:

• https://github.com/arxanas/git-branchless/pull/1353
• https://github.com/arxanas/git-branchless/pull/1354
• https://github.com/arxanas/git-branchless/pull/1355
• https://github.com/arxanas/git-branchless/pull/1356
• https://github.com/arxanas/git-branchless/pull/1202
• https://github.com/arxanas/git-branchless/pull/1357
• https://github.com/arxanas/git-branchless/pull/1358

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refactor(core): re-export formatting symbols from cursive_core

This should have been done from the beginning, since we operate on these symbols in several places for formatting. This would also help a migration away from cursive, since now only two modules have direct dependencies on cursive/cursive_core:

• git-branchless-lib for general output formatting.
• git-branchless-undo for the interactive undo UI.