3fb09b9889665a24b34f25e9d1385a05058a28b7 Warn unrecognized sections in the config file (Akio Nakamura)
Pull request description:
This PR intends to resolve #14702.
In the config file, sections are specified by square bracket pair "[]"$,
or included in the option name itself which separated by a period"(.)".
Typicaly, [testnet] is not a correct section name and specified options
in that section are ignored but user cannot recognize what is happen.
So, add some log-warning messages if unrecognized section names are
present in the config file after checking section only args.
note: Currentry, followings are out of scope of this PR.
1) Empty section name or option name can describe.
e.g. [] , .a=b, =c
2) Multiple period characters can exist in the section name and option name.
e.g. [c.d.e], [..], f.g.h.i=j, ..=k
Tree-SHA512: 2cea02a0525feb40320613989a75cd7b7b1bd12158d5e6f3174ca77e6a25bb84425dd8812f62483df9fc482045c7b5402d69bc714430518b1847d055a2dc304b
---
This is a backport of Core PR14708