restructure: align module folder layout with score module folder structure

[umaucher]

Aligns persistency with the score module folder structure DR (eclipse-score/score#3194): the module-level src folder is optional and dropped, and language-split folders (cpp/rust) are replaced by a per-component layout.

• score/kvs/ now holds the public C++ interface directly (no src/ wrapper); internal/, rust_kvs/, rust_kvs_tool/ are the component's <lower_level_comp> folders.
• score/kvs/tests/ holds both the C++ unit tests and the integration test suites (test_scenarios/, test_cases/, integration_test_scenarios/), since this module has a single component and those suites test it specifically rather than spanning multiple components.
• Updated every Bazel target, CI workflow, Cargo/pytest config, and doc that referenced the old src//tests/ paths, including the targets newly introduced by coverage: adopt the unified LLVM coverage pipeline from score_tooling 2.1.1 #380 (quality/coverage, coverage.yml, release.yml).

Note: release.yml's "Run Unit Test with Coverage for Rust" step already called a //:rust_coverage target that no longer exists after #380 removed it in favour of the unified coverage pipeline — that regression predates this PR and is left untouched here as out of scope.

[github-actions]

License Check Results

🚀 The license check job ran with the Bazel command:

bazel run --lockfile_mode=error //:license-check

Status: ⚠️ Needs Review

Click to expand output

[License Check Output]
Extracting Bazel installation...
Starting local Bazel server (8.6.0) and connecting to it...
INFO: Invocation ID: 049285db-ab4c-41b9-a421-1d07e0521f4f
Computing main repo mapping: 
Computing main repo mapping: 
Computing main repo mapping: 
Computing main repo mapping: 
Loading: 
Loading: 3 packages loaded
Loading: 3 packages loaded
    currently loading: 
Loading: 3 packages loaded
    currently loading: 
Loading: 3 packages loaded
    currently loading: 
Loading: 3 packages loaded
    currently loading: 
Loading: 3 packages loaded
    currently loading: 
Analyzing: target //:license-check (4 packages loaded, 0 targets configured)
Analyzing: target //:license-check (4 packages loaded, 0 targets configured)

Analyzing: target //:license-check (67 packages loaded, 10 targets configured)

Analyzing: target //:license-check (90 packages loaded, 10 targets configured)

Analyzing: target //:license-check (141 packages loaded, 622 targets configured)

Analyzing: target //:license-check (149 packages loaded, 3125 targets configured)

Analyzing: target //:license-check (149 packages loaded, 3125 targets configured)

Analyzing: target //:license-check (149 packages loaded, 3125 targets configured)

Analyzing: target //:license-check (159 packages loaded, 6212 targets configured)

Analyzing: target //:license-check (166 packages loaded, 9321 targets configured)

Analyzing: target //:license-check (166 packages loaded, 9321 targets configured)

Analyzing: target //:license-check (172 packages loaded, 9366 targets configured)

Analyzing: target //:license-check (176 packages loaded, 11384 targets configured)

INFO: Analyzed target //:license-check (177 packages loaded, 11510 targets configured).
INFO: From Generating Dash formatted dependency file ...:
INFO: Successfully converted 66 packages from Cargo.lock to bazel-out/k8-fastbuild/bin/formatted.txt
[15 / 17] [Prepa] JavaToolchainCompileBootClasspath external/rules_java+/toolchains/platformclasspath.jar
[16 / 17] Building license.check.license_check.jar (); 0s disk-cache, multiplex-worker
INFO: Found 1 target...
Target //:license.check.license_check up-to-date:
  bazel-bin/license.check.license_check
  bazel-bin/license.check.license_check.jar
INFO: Elapsed time: 31.152s, Critical Path: 2.41s
INFO: 17 processes: 12 internal, 4 processwrapper-sandbox, 1 worker.
INFO: Build completed successfully, 17 total actions
INFO: Running command line: bazel-bin/license.check.license_check ./formatted.txt <args omitted>
usage: org.eclipse.dash.licenses.cli.Main [-batch <int>] [-cd <url>]
       [-confidence <int>] [-ef <url>] [-excludeSources <sources>] [-help] [-lic
       <url>] [-project <shortname>] [-repo <url>] [-review] [-summary <file>]
       [-timeout <seconds>] [-token <token>]

[umaucher]

all the failed jobs triggered by pull_request_target need to fail since they use the "old" main workflows pointing to the outdated targets. The ones triggered by pull_request newly added are green.

[umaucher]

the generated documentation is in https://eclipse-score.github.io/persistency/pr-386/index.html