Make indexing a stable feature

[vinistock]

Motivation

We've had a few releases with indexing as experimental and fixed all issues encountered so far. Let's make indexing stable and get definition, workspace symbol and hover in the hands of devs.

Implementation

Just removed the experimental checks.

Automated Tests

Since we push progress notifications, some tests had to be adapted to account for those.

[github-actions]

Benchmark results in seconds (slowest at top)

          textDocument/completion average: 0.23488 std_dev: 0.004221
          textDocument/diagnostic average: 0.048863 std_dev: 0.01139
          textDocument/definition average: 0.005518 std_dev: 0.003203
      textDocument/selectionRange average: 0.004854 std_dev: 0.000656
   textDocument/documentHighlight average: 0.003065 std_dev: 0.000282
      textDocument/documentSymbol average: 0.002972 std_dev: 0.000243
            textDocument/codeLens average: 0.002939 std_dev: 0.000187
        textDocument/documentLink average: 0.002922 std_dev: 0.000319
        textDocument/foldingRange average: 0.002919 std_dev: 0.000192
 textDocument/semanticTokens/full average: 0.002902 std_dev: 0.000254
textDocument/semanticTokens/range average: 0.001921 std_dev: 0.000178
               codeAction/resolve average: 0.001699 std_dev: 0.000182
           textDocument/inlayHint average: 0.001628 std_dev: 0.000101
               textDocument/hover average: 0.001627 std_dev: 0.000115
    textDocument/onTypeFormatting average: 0.000989 std_dev: 7.6e-05
          textDocument/formatting average: 0.000964 std_dev: 0.000331
          textDocument/codeAction average: 0.000955 std_dev: 9.2e-05


================================================================================
Comparison with main branch:

 textDocument/semanticTokens/full unchanged
textDocument/semanticTokens/range unchanged
      textDocument/documentSymbol unchanged
        textDocument/foldingRange unchanged
          textDocument/formatting unchanged
          textDocument/diagnostic unchanged
        textDocument/documentLink unchanged
           textDocument/inlayHint unchanged
      textDocument/selectionRange unchanged
   textDocument/documentHighlight unchanged
               textDocument/hover unchanged
          textDocument/codeAction unchanged
    textDocument/onTypeFormatting unchanged
               codeAction/resolve unchanged
          textDocument/completion unchanged
            textDocument/codeLens unchanged
          textDocument/definition unchanged


================================================================================
Missing benchmarks:

RubyLsp::Requests::ShowSyntaxTree