Upgrade to latest Langium version

[martin-fleck-at]

• Adapt to latest version of Langium
• Re-use indentation-based parsing provided by Langium
• Rework serialization
• Apply and deactivate async threaded parsing as it crashes on error

[github-actions[bot]]

Unit Test Results

 3 files  ±  0  18 suites   - 12   2m 20s :stopwatch: +8s 25 tests  -  46  25 :white_check_mark:  -  46  0 :zzz: ±0  0 :x: ±0  75 runs   - 141  75 :white_check_mark:  - 141  0 :zzz: ±0  0 :x: ±0 

Results for commit 0a66c57f. ± Comparison against base commit a48eac6d.

This pull request removes 46 tests.

``` CrossModelLexer Indentation Simple indentation, should give indent and dedent token ‑ CrossModelLexer Indentation Simple indentation, should give indent and dedent token CrossModelLexer Indentation double indentation, but dedent in text ‑ CrossModelLexer Indentation double indentation, but dedent in text CrossModelLexer Indentation double indentation, should give indent and dedent token ‑ CrossModelLexer Indentation double indentation, should give indent and dedent token CrossModelLexer Indentation single indentation but stay on same level, should give 1 indent and 1 dedent token ‑ CrossModelLexer Indentation single indentation but stay on same level, should give 1 indent and 1 dedent token CrossModelLexer Simple keywords should tokenize a couple of simple words ‑ CrossModelLexer Simple keywords should tokenize a couple of simple words CrossModelLexer Simple keywords should tokenize a simple word ‑ CrossModelLexer Simple keywords should tokenize a simple word CrossModelTokenBuilder buildTokens Should give DEDENT token in second spot ‑ CrossModelTokenBuilder buildTokens Should give DEDENT token in second spot CrossModelTokenBuilder buildTokens Should give INDENT token in third spot ‑ CrossModelTokenBuilder buildTokens Should give INDENT token in third spot CrossModelTokenBuilder buildTokens Should give NEWLINE token in first spot ‑ CrossModelTokenBuilder buildTokens Should give NEWLINE token in first spot CrossModelTokenBuilder buildTokens Should give SPACE token in last spot ‑ CrossModelTokenBuilder buildTokens Should give SPACE token in last spot … ```

:recycle: This comment has been updated with latest results.

[martin-fleck-at]

This is partially based on https://github.com/CrossBreezeNL/crossmodel/pull/63 and needs to be rebased once the other PR is merged. This is why it is still in draft stage.