BP-69: Allow caller to pass a parent slog Logger to created/opened ledgers

[merlimat]

Summary

Add withLoggerContext(Logger parentLogger) to CreateBuilder and OpenBuilder so an application that already has a per-request / per-tenant slog Logger can pass it as the parent of the per-handle Logger that bookkeeper builds. The LedgerHandle's logger inherits the parent's context via slog's LoggerBuilder.ctx(Logger), then layers on the always-present ledgerId.

// Application's per-request logger, built once at the top of a request.
Logger requestLog = Logger.get(MyService.class).with()
        .attr("requestId", requestId)
        .attr("tenant", tenantId)
        .build();

WriteHandle writer = bk.newCreateLedgerOp()
        .withEnsembleSize(3).withWriteQuorumSize(3).withAckQuorumSize(2)
        .withPassword(pw)
        .withLoggerContext(requestLog)   // ← new
        .execute().get();

// Every log statement emitted by the writer (and the create-time machinery
// that produced it) now carries requestId, tenant, and ledgerId.

Passing a Logger (vs. a Map<String, Object>) avoids the need to extract / serialize attrs out of slog: the application's Logger is the natural source of context.

Implementation

• New default no-op method on the @Public / @Unstable CreateBuilder and OpenBuilder interfaces — preserves source compatibility for any out-of-tree implementor.
• CreateBuilderImpl and OpenBuilderBase store the parent Logger and pass it through to LedgerCreateOp / LedgerOpenOp, which forward it to the LedgerHandle / LedgerHandleAdv / ReadOnlyLedgerHandle constructor.
• New constructor overloads on the three handle types take a Logger parentLogger; existing constructors delegate with null.
• LedgerOpenOp's own contextual log is built with the same parent so log events emitted during the open path also carry the attrs.

Test plan

New LoggerContextTest covers:

• Compile-time API contract: withLoggerContext(Logger) on both builders is chainable and returns the same builder type.

• Runtime: passing null is a no-op; non-null context map executes cleanly through to WriteHandle.getId().

• Open-on-non-existent-ledger end-to-end test under a log4j2 capturing appender.

• Deterministic unit test of the slog LoggerBuilder.ctx(parent).attr("ledgerId", ...).build() chain — verifies the parent's attrs and ledgerId both appear in event.getContextData() on the resulting Logger.

• mvn -pl bookkeeper-server compile checkstyle:check clean

• LoggerContextTest (5 tests) pass locally

• Existing BookKeeperBuildersTest / BookKeeperBuildersOpenLedgerTest (33 tests) unaffected

• Full CI matrix green