Backported changes from the default exim config

[StudioMaX]

Changes:

hostlist relay_from_hosts = localhost
instead of
hostlist relay_from_hosts = 127.0.0.1
because of
Exim/exim@ff28412
https://github.com/Exim/exim/pull/1/files

Removed

rfc1413_hosts = *
rfc1413_query_timeout = 5s

because of
Exim/exim@f926e27#diff-3489bb4734f2a6f27caffbaedb4bd782

Added (to modern OS)
prdr_enable = true
because of
Exim/exim@ff1c79b
https://www.exim.org/exim-html-current/doc/html/spec_html/ch-access_control_lists.html#SECTPRDRACL

Removed from this PR, see comments

acl_check_data:
  deny   message        = maximum allowed line length is 998 octets, \
                          got $max_received_linelength
         condition      = ${if > {$max_received_linelength}{998}}
remote_smtp:
  message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}

because of
Exim/exim@8c95212
Exim/exim@adb278a

Added

dnslookup:
  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8

because of (security breach?)
http://www.exim.org/exim-html-3.20/doc/html/spec_27.html#SEC687

[StudioMaX]

Deleted these checks despite the fact that this is required by RFC.

acl_check_data:
  deny   message        = maximum allowed line length is 998 octets, \
                          got $max_received_linelength
         condition      = ${if > {$max_received_linelength}{998}}
remote_smtp:
  message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}

The reason for adding them in the original config: https://bugs.exim.org/show_bug.cgi?id=1684

I myself ran into the problem because of this rule.
On Amazon Simple Notification Service (SNS) I set the email address from my server as the recipient of notifications about bounced emails that are sent via Amazon Simple Email Service (SES). And for a few days I cannot understand why I did not receive these bounce messages - it turned out that Amazon SNS sends an email, and does not comply with this rule about 998 characters per line.

[Neustradamus]

Dear all,

@Dennis-SEG has done a very good job here:

• Complete modernization: PHP 8.0-8.4 support, React 18, and security hardening #2322

What do you think?