Fix a number of clang-tidy detected defects

[jblomer]

A test run of clang-tidy on the RNTuple code with the following checks

Checks: 'bugprone-*,-bugprone-assignment-in-if-condition,-bugprone-branch-clone,-bugprone-derived-method-shadowing-base-method,-bugprone-easily-swappable-parameters,-bugprone-implicit-widening-of-multiplication-result,-bugprone-incorrect-enable-if,-bugprone-macro-parentheses,-bugprone-multi-level-implicit-pointer-conversion,-bugprone-narrowing-conversions,-bugprone-not-null-terminated-result,-bugprone-random-generator-seed,-bugprone-reserved-identifier,-bugprone-signed-char-misuse,-bugprone-std-namespace-modification,-bugprone-switch-missing-default-case,-bugprone-throwing-static-initialization,-bugprone-too-small-loop-variable,-bugprone-unchecked-optional-access,-bugprone-unhandled-self-assignment,-bugprone-unused-return-value,-bugprone-virtual-near-miss,cppcoreguidelines-virtual-class-destructor,misc-*,-misc-non-private-member-variables-in-classes,-misc-include-cleaner,-misc-misplaced-const,-misc-multiple-inheritance,-misc-no-recursion,misc-non-copyable-objects,-misc-non-private-member-variables-in-classes,-misc-predictable-rand,-misc-unconventional-assign-operator,-misc-use-anonymous-namespace,performance-*,-performance-enum-size,-performance-inefficient-string-concatenation,-performance-no-int-to-ptr,-performance-noexcept-swap,readability-duplicate-include,readability-delete-null-pointer,readability-misleading-indentation,readability-redundant-control-flow,readability-redundant-declaration,readability-redundant-function-ptr-dereference,readability-reference-to-constructed-temporary'