SAConnection twophase methods are broken

[gistart]

Describe the bug

1. begin_twophase() is not a context manager
2. recover_twophase() is broken
3. rollback_prepared() is broken

To Reproduce

just use these methods)

Expected behavior

1. begin_twophase() behaves as a context manager, using commit_prepared() at the end OR docs changed to reflect current implementation
2. does not crash on accessing ResultProxy
3. does not crash on string formatting

Logs/tracebacks

1. begin_context() is not a context

According to docs: https://aiopg.readthedocs.io/en/stable/sa.html#aiopg.sa.SAConnection.begin_twophase

coroutine async-with begin_twophase(xid=None)

but in reality:

    async with conn.begin_twophase() as transaction:
AttributeError: __aenter__

2. recover_twophase() is broken

result is not awaited:

  File "/Users/ovmikhaylov/work/aiopg/aiopg/sa/connection.py", line 363, in recover_twophase
    return [row[0] for row in result]
TypeError: 'ResultProxy' object is not iterable

3. rollback_prepared() is broken

Due to error in f-string:

  File "/Users/ovmikhaylov/work/aiopg/aiopg/sa/connection.py", line 368, in rollback_prepared
    await self.execute(f"ROLLBACK PREPARED {xid:!r}")
ValueError: Invalid format specifier

Python Version

3.10

aiopg Version

1.3.3

OS

Darwin gmbp.local 20.6.0 Darwin Kernel Version 20.6.0: Tue Oct 12 18:33:42 PDT 2021; root:xnu-7195.141.8~1/RELEASE_X86_64 x86_64

Additional context

No response

Code of Conduct

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