IDEA-83937 Unable to commit with unicode message - Mercurial

*charset updated from HGENCODING or from Project encoding settings
*test added
*system constants removed
(cherry picked from commit 51b62b4ed1c780708b82bd56dcc1c345f07b471c)
HGENCODING var introduced in HgVcs;  getDefaultEncoding simplified; annotations for charset added
(cherry picked from commit ec21af72249dd55614b7b72a38355178265c0391)
Encoding information provided for each hg command via '--encoding' arg

*define appropriate encoding using HGENCODING var or EncodingProjectManager;
*encoding args need to be provided because branch names and other strings in mercurial response can contain non-ascii symbols (using utf-8 or 'local' string encoding)
(cherry picked from commit 9b949de45284455ef87e96c208da14db17743a87)
Encoding test added for special characters in commit message.
(cherry picked from commit f634015808cebd13cdddb190116b0b276aeaa5e1)
Encoding test changed: using hgLogCommand instead of HgCachingCommitedChangesProvider
(cherry picked from commit 38b3b3625aaf94e5cf894be79e610c1bc74d137a)
encoding tests for 129  fixed