This commit introduces Micrometer as an API dependency to the spring-web
module. Micrometer is used here to instrument `RestTemplate` and record
`Observation` for HTTP client exchanges.
This will replace Spring Boot's `MetricsClientHttpRequestInterceptor`
which uses the request interceptor contract for instrumentation.
This approach is limited as measurements and tags aren't always precise
and overhead is more important than a direct instrumentation.
See gh-28341
a0ddcd07c8