hdf5_msb

Add a log outlet for metadata cache (MDC) invalidations,
`mdc_invalidation`, and use it to log a message when
H5C_evict_or_refresh_all_entries_in_page() does not find any affected
entries.

Pass a page length to H5C_evict_or_refresh_all_entries_in_page() so that
it can assert if a multipage eviction overlaps a single-page entry,
which had better not happen.

Fix a bug in H5F_vfd_swmr_reader_end_of_tick() and heavily rework it:
remove page-table entries and evict/refresh MDC entries that overlap
*added* shadow-index entries.  Because we didn't do that before, in the
zoo test, the reader didn't see all of the changes made by the writer
until the writer closed the file:  MDC entries covered the new content
in the shadow file.

In H5F_vfd_swmr_reader_end_of_tick(), log changes to the shadow index
with the new outlet, `shadow_index_update`.

Convert a some of John's disused diagnostic printfs to an
`hlog_fast(eot, ...)` call.