cloud_storage: Extend fast trim cleanup to new segment name

When a log segment is removed in fast trim, the associated index and tx
files are also removed. This commit extends this feature to new log
segment name formats, which may contain a term after the name.

src/v/cloud_storage/cache_service.cc

@@ -529,6 +529,8 @@ ss::future<cache::trim_result> cache::trim_fast(
     trim_result result;
 
     size_t candidate_i = 0;
+    const std::regex segment_expr{
+      R"#(.*\.log(\.\d+)?)#", std::regex_constants::optimize};
     while (
       candidate_i < candidates.size()
       && (result.deleted_size < size_to_delete || result.deleted_count < objects_to_delete)) {
@@ -568,7 +570,7 @@ ss::future<cache::trim_result> cache::trim_fast(
             std::optional<std::string> tx_file;
             std::optional<std::string> index_file;
 
-            if (std::string_view(file_stat.path).ends_with(".log")) {
+            if (std::regex_match(file_stat.path.data(), segment_expr)) {
                 // If this was a legacy whole-segment item, delete the index
                 // and tx file along with the segment
                 tx_file = fmt::format("{}.tx", file_stat.path);

src/v/cloud_storage/tests/cache_test.cc

@@ -500,3 +500,41 @@ FIXTURE_TEST(test_exhaustive_trim_runs_after_fast_trim, cache_test_fixture) {
           return !std::filesystem::exists(path);
       }));
 }
+
+FIXTURE_TEST(test_log_segment_cleanup, cache_test_fixture) {
+    std::vector<std::filesystem::path> objects{
+      CACHE_DIR / "test.log.1",
+      CACHE_DIR / "test.log.1.index",
+      CACHE_DIR / "test.log.1.tx",
+      CACHE_DIR / "test.log",
+      CACHE_DIR / "test.log.index",
+      CACHE_DIR / "test.log.tx"};
+    for (const auto& obj : objects) {
+        std::ofstream f{obj};
+        f.flush();
+    }
+
+    // An un-removable file makes sure the fast trim will have to remove the two
+    // segment files.
+    {
+        std::ofstream f{CACHE_DIR / "accesstime"};
+        f.flush();
+    }
+
+    BOOST_REQUIRE(
+      std::all_of(objects.cbegin(), objects.cend(), [](const auto& path) {
+          return std::filesystem::exists(path);
+      }));
+
+    clean_up_at_start().get();
+
+    // With this limit all of the index+tx files should not have to be removed,
+    // but fast trim will remove all of these files after removing the two
+    // segments.
+    trim_cache(std::nullopt, 4);
+
+    BOOST_REQUIRE(
+      std::all_of(objects.cbegin(), objects.cend(), [](const auto& path) {
+          return !std::filesystem::exists(path);
+      }));
+}