MDEV-18115 Remove dummy tablespace for the redo log

Redo log subsystem was decoupled from tablespace subsystem. It now manages file
descriptors for redo log files by itself.

FIL_TYPE_LOG: removed, code in various places was simplified

SRV_LOG_SPACE_FIRST_ID: renamed to SRV_SPACE_ID_UPPER_BOUND
  to better match its purpose. Code in various places was simplified

fil_n_log_flushes: replaced with log_sys::flushes
fil_n_pending_log_flushes: replaced with log_sys::pending_flushes

log_t::files::files: redo log file descriptors
log_t::files::file_names: redo log file names

log_t::files::set_file_names(): set file names without opening them
log_t::files::open_files(): opens redo log files
log_t::files::read(): treats several files as one big
log_t::files::write(): treats several files as one big
log_t::files::fsync(): flushes page cache to disk
log_t::files::close_files(): closes redo log files

fil_open_log_and_system_tablespace_files(): renamed to fil_open_system_tablespace_files()
  and obviously it now doesn't open redo log files

global files[1000]: removed. Why it was needed at all?

0 files changed, 0 insertions, 0 deletions