feat: Add support to unsubscribe from BLE advertisements

[richardhopton]

What does this implement/fix?

Adds support to unsubscribe from BLE advertisements. At the moment after subscribing, the messages will be sent over the API connection even if they are ignored by the client.

Types of changes

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other

Related issue or feature (if applicable): fixes

Pull request in esphome-docs with documentation (if applicable): esphome/esphome-docs#

Test Environment

• ESP32
• ESP32 IDF
• ESP8266
• RP2040

Example entry for config.yaml:

# Example config.yaml

Checklist:

• The code change is tested and works locally.
• Tests have been added to verify that the new code works (under tests/ folder).

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in esphome-docs.

[probot-esphome]

Hey there @OttoWinter, mind taking a look at this pull request as it has been labeled with an integration (api) you are listed as a code owner for? Thanks!
_{^{(message by CodeOwnersMention)}}

[richardhopton]

@jesserockz as per our discord conversation