remote: plug memory leaks

remote: plug memory leaks

The in-core data structure used to keep track of
'url.<real>.{insteadOf,pushInsteadOf} = <alias>' settings is not
properly cleaned up when the process is done with it.

'struct rewrites' is embedded in 'remote_state' and serves as the
top level of the rewrite data.  This holds an array of a variable
number of pointers to 'struct rewrite' allocated individually on the
heap.  Each 'struct rewrite' holds a '.base' string and an array of
'struct counted_string' called '.instead_of', which is allocated
contiguously on the heap.  Each 'struct counted_string' has a
pointer to a string allocated on the heap.

Amid these pointers, rewrites_release() fails to free everything
other than 'struct rewrite''s '.base' member and the 'struct rewrite'
instances themselves.

Fix rewrites_release() to also free the contiguous array storing
'.instead_of', the string pointers within each '.instead_of' element,
and each 'struct rewrite' instance individually allocated on the heap.

Signed-off-by: Junio C Hamano <redacted>