feat: add micrometer support

[PhilippHeuer]

Prerequisites for Code Changes

• This pull request follows the code style of the project
• I have tested this feature

Description

micrometer is a facade for metric collection, the goal is to provide metrics from all t4j components in a agnostic / easy way to improve observability.

Changes Proposed

• use the feign-bom instead
• metrics for all http clients (feign-micrometer for http request / response metrics)
• metrics for client-websocket
• metrics for chat
• pubsub
• pool metrics (connection count, ...)

Out-of-Scope

• apollo (graphql)

Additional Information

Can use the following when testing locally to print collected metrics every 10s:
MeterRegistry meterRegistry = new CompositeMeterRegistry(Clock.SYSTEM, Collections.singletonList(new LogMetricsRegistry()));

Chat

meterRegistry.gauge("twitch4j_chat_latency",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), latency);
meterRegistry.gauge("twitch4j_chat_channel_count",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), getChannels().size());
meterRegistry.gauge("twitch4j_chat_bucket",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId), Tag.of("bucket", "irc_message")), ircMessageBucket.getAvailableTokens());
meterRegistry.gauge("twitch4j_chat_bucket",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId), Tag.of("bucket", "whisper_message")), ircWhisperBucket.getAvailableTokens());
meterRegistry.gauge("twitch4j_chat_bucket",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId), Tag.of("bucket", "auth")), ircAuthBucket.getAvailableTokens());
meterRegistry.gauge("twitch4j_chat_bucket",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId), Tag.of("bucket", "join")), ircJoinBucket.getAvailableTokens());
meterRegistry.gauge("twitch4j_chat_message_queue_count",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), ircCommandQueue.size());

PubSub

meterRegistry.gauge("twitch4j_pubsub_latency",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), latency);
meterRegistry.gauge("twitch4j_pubsub_topic_count",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), subscribedTopics.size());
meterRegistry.gauge("twitch4j_pubsub_queue_count",  Arrays.asList(Tag.of("connection_name", connectionName), Tag.of("connection_id", connectionId)), commandQueue.size());

Connection Pools

meterRegistry.gauge("twitch4j_chat_pool_connection_count", Collections.singletonList(Tag.of("connection_name", connectionName)), numConnections());
meterRegistry.gauge("twitch4j_chat_pool_subscription_count", Collections.singletonList(Tag.of("connection_name", connectionName)), numSubscriptions());