[BOLT] Compress YAML pseudo probe information

[aaupov]

Introduce an optional value compact for profile-write-pseudo-probes flag,
enabling compressed encoding of pseudo probe information in YAML profile:

• block probes are encoded into space-separated list of probes grouped by
  inline tree nodes in format [probes]_[nodes]:
  • probes and nodes are comma-separated indices,
  • contiguous spans [from,...,to] are coalesced into from^run_length,
  • probes, nodes, and run lengths are base36-encoded,
  • omissions: head probe (index = 1), root node (node = 0).
• inline tree is encoded into space-separated list of node descriptions
  using base36-encoding.
• the character set is selected to avoid quoting.

This significantly reduces the size of YAML profile and makes parsing faster
(as it replaces nested FlowVectors with strings).

Test Plan: for Clang, the profile size is reduced from 241M to 140MB.

TBD: compress pseudo_probe_desc. Use DFS for probes, and BFS for inline tree.
Measure emission and parsing time.

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff origin/main HEAD --extensions h,cpp -- bolt/include/bolt/Profile/ProfileYAMLMapping.h bolt/include/bolt/Profile/YAMLProfileWriter.h bolt/include/bolt/Utils/CommandLineOpts.h bolt/lib/Profile/DataAggregator.cpp bolt/lib/Profile/YAMLProfileReader.cpp bolt/lib/Profile/YAMLProfileWriter.cpp bolt/lib/Rewrite/PseudoProbeRewriter.cpp --diff_from_common_commit

⚠️
The reproduction instructions above might return results for more than one PR
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changing origin/main to the base branch/commit you want to compare against.
⚠️

View the diff from clang-format here.

diff --git a/bolt/lib/Profile/YAMLProfileWriter.cpp b/bolt/lib/Profile/YAMLProfileWriter.cpp
index 1667026a8..99d42c4c9 100644
--- a/bolt/lib/Profile/YAMLProfileWriter.cpp
+++ b/bolt/lib/Profile/YAMLProfileWriter.cpp
@@ -486,7 +486,7 @@ std::error_code YAMLProfileWriter::writeProfile(const RewriteInstance &RI) {
   // Add probe inline tree nodes.
   InlineTreeDesc InlineTree;
   if (const MCPseudoProbeDecoder *Decoder =
-      opts::ProfileWritePseudoProbes ? BC.getPseudoProbeDecoder() : nullptr)
+          opts::ProfileWritePseudoProbes ? BC.getPseudoProbeDecoder() : nullptr)
     std::tie(BP.PseudoProbeDesc, InlineTree) = convertPseudoProbeDesc(*Decoder);
 
   // Add all function objects.