[insteon] Use separate pool for long running threads

[jsetton]

This change adds a separate pool for long running threads.

This should be backported as the binding is unable to successfully download the modem database for some users, preventing the initialization process from completing.

[lolodomo]

LGTM, thank you

[lolodomo]

@jsetton : can be backported to 4.3.x with no risk?

[jsetton]

No risk. I have been testing with users on 4.3 actually.

[jsetton]

@lolodomo were you able to backport this change?

[lolodomo]

Cherry-picking this PR in 4.3.x branch leads to conflicts:

$ git cherry-pick 247495335e7c41e4a0edd753b152ad54d70f27de
Auto-merging bundles/org.openhab.binding.insteon/src/main/java/org/openhab/binding/insteon/internal/handler/InsteonLegacyNetworkHandler.java
CONFLICT (content): Merge conflict in bundles/org.openhab.binding.insteon/src/main/java/org/openhab/binding/insteon/internal/handler/InsteonLegacyNetworkHandler.java
Auto-merging bundles/org.openhab.binding.insteon/src/main/java/org/openhab/binding/insteon/internal/handler/InsteonBridgeHandler.java
CONFLICT (content): Merge conflict in bundles/org.openhab.binding.insteon/src/main/java/org/openhab/binding/insteon/internal/handler/InsteonBridgeHandler.java
Auto-merging bundles/org.openhab.binding.insteon/src/main/java/org/openhab/binding/insteon/internal/handler/InsteonBaseThingHandler.java
error: could not apply 247495335e... [insteon] Use separate pool for long running threads (#18147)
hint: after resolving the conflicts, mark the corrected paths
hint: with 'git add <paths>' or 'git rm <paths>'
hint: and commit the result with 'git commit'

I aborted.

[jsetton]

@lolodomo You can use jsetton@bd3ca77

The conflicts are related to #17922.

[lsiepel]

Patched by #18279