* Fix maxMessagesPerPoll for SourcePollingChAdapter
The `AbstractMethodAnnotationPostProcessor` does not check
for `PollerMetadata.MAX_MESSAGES_UNBOUNDED` before setting
`maxMessagesPerPoll` into a `SourcePollingChannelAdapter`
which in this case must be `1`
Also fix `SourcePollingChannelAdapterFactoryBean` to not mutate
the provided `PollerMetadata` (which might be global default)
with a new `maxMessagesPerPoll`
**Cherry-pick to `6.1.x` & `6.0.x`**
* * Fix `this.` prefix in `SourcePollingChannelAdapterFactoryBean`
8c146d562d