rtabmap_slam tests and doc (#1460)

* rtabmap_slam tests and doc

* another round of review of the doc

* Disable by default use_intra_process_comms on latched/transient publishers

* Added test to catch not unlocked mutex from early error exit

* updated coverage settings

* Using UScopeMutex on all tryLock()

.github/lcovrc

@@ -0,0 +1,45 @@
+# lcov configuration for .github/workflows/coverage.yml.
+#
+# A copy of colcon-lcov-result 0.5.0's default (colcon_lcov_result/verb/configuration/lcovrc),
+# with branch coverage turned off below. The whole file is needed: --lcov-config-file
+# replaces the default rather than adding to it.
+#
+# Why no branch coverage: gcc emits a hidden "it threw" branch on nearly every line that
+# calls a function, and no test takes it. Each such line -- a declaration like
+# 'rtabmap::Transform t;' included -- then counts as a partial, and Codecov reports a
+# partial line as not covered. lcov's geninfo_no_exception_branch would drop those
+# branches, but not with the lcov 1.15 of Ubuntu 22.04 and gcc 11: its JSON reader
+# ignores the flag, and its text reader cannot read gcc 11's .gcno files. So only line
+# coverage is reported: a line is covered when a test ran it.
+
+geninfo_auto_base=1
+
+# Specify size of tabs
+genhtml_num_spaces = 2
+
+# Include color legend in HTML output if non-zero
+genhtml_legend = 1
+
+# Include function coverage data display
+genhtml_function_coverage = 1
+
+# Include branch coverage data display
+genhtml_branch_coverage = 0
+
+# Specify whether to capture coverage data for external source
+# files
+geninfo_external = 0
+
+# Less verbose output
+lcov_quiet = 1
+
+# Specify if function coverage data should be collected and
+# processed.
+lcov_function_coverage = 1
+
+# Specify if branch coverage data should be collected and
+# processed.
+lcov_branch_coverage = 0
+
+## Follow symlinks
+lcov_follow = 1