Add resilience4j-circuit-breaker: Resilience4j 2.4.0 vs Spring Framework 7 core, on Boot 4.1

Companion module for the rewritten post 'Resilience4j Circuit Breaker in Spring Boot 4.1:
What It's Still For', reworked around Framework 7 now shipping @Retryable/@ConcurrencyLimit
in core. Covers what's still Resilience4j's job (circuit breaker, rate limiter, bulkhead's
bounded wait, fallback methods, Actuator/Micrometer metrics), the off-by-one between
maxAttempts and maxRetries, and two Boot-4.1 build breaks: spring-boot-starter-aop no longer
exists (renamed to spring-boot-starter-aspectj, proven with Maven Central metadata and the
renamed starter's own POM -- see resilience/docs/08-starter-aop-renamed-to-starter-aspectj.md
in this same repo), and the resulting fix uses that renamed starter directly rather than
assembling spring-aop + aspectjweaver by hand. Kept as its own module rather than a new
top-level repository, alongside the existing resilience/ module for the sibling Framework-7
post.

resilience4j-circuit-breaker/docs/output/03e-r4j-retry-exhaustion.txt

@@ -0,0 +1,8 @@
+Resilience4j @Retry(maxAttempts=3) against a permanently-dead downstream: counting convention
+=============================================================================================
+maxAttempts=3, downstream permanently down
+downstream calls before giving up: 3
+Resilience4j's maxAttempts is the TOTAL call count (initial attempt included): 3, not 4.
+Core's @Retryable(maxRetries=3) is 3 retries AFTER the initial attempt: 4 total
+(see docs/output/03b-retryable-no-memory.txt). Same-sounding config, different arithmetic --
+porting a maxRetries value from one to the other by name alone is off by one.