C++: Make implicit this receivers explicit

[kaspersv]

Make all implicit this call receivers explicit to align with internal style guidelines.

Automatically generated from results of QL-for-QL implicit this query as follows:

$CODEQL database create $LANG-db -l ql -s $CODEQL_PATH/$LANG/ql --search-path $CODEQL_PATH/ql/extractor-pack
$CODEQL database analyze $LANG-db --format=csv --output=$LANG $CODEQL_PATH/ql/ql/src/queries/style/ImplicitThis.ql
python3 insert-explicit-this.py $LANG $CODEQL_PATH/$LANG/ql $CODEQL

using the insert-explicit-this.py script to interpret the results and insert explicit this receivers.

[jketema]

LGTM