bump MSRV to 1.64 and indexmap to 2.0

[shaun-cox]

Due to requirement of #1199, this is a separate PR to bump MSRV.
Contributing factors:

• tokio now has MSRV of 1.63
• we're using older indexmap 1.18, and indexmap 2.0 has MSRV of 1.64

Changes

• bump MSRV to 1.64
• bump indexmap to 2.0
• fix newly exposed lint about deriving Default instead of manually implementing

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

Patch coverage: 24.4% and no project coverage change.

Comparison is base (7607ad3) 49.6% compared to head (b8b816c) 49.7%.
Report is 6 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1203   +/-   ##
=====================================
  Coverage   49.6%   49.7%           
=====================================
  Files        164     172    +8     
  Lines      20653   20710   +57     
=====================================
+ Hits       10258   10301   +43     
- Misses     10395   10409   +14     

Files Changed	Coverage Δ
opentelemetry-api/src/lib.rs	100.0% <ø> (ø)
opentelemetry-api/src/order_map.rs	4.2% <0.0%> (ø)
...emetry-jaeger/src/exporter/config/collector/mod.rs	51.6% <ø> (ø)
opentelemetry-jaeger/src/lib.rs	95.3% <ø> (ø)
opentelemetry-otlp/src/exporter/grpcio/logs.rs	0.0% <0.0%> (ø)
opentelemetry-otlp/src/exporter/grpcio/mod.rs	35.4% <0.0%> (ø)
opentelemetry-otlp/src/exporter/grpcio/trace.rs	0.0% <0.0%> (ø)
opentelemetry-otlp/src/exporter/http/logs.rs	0.0% <0.0%> (ø)
opentelemetry-otlp/src/exporter/http/metrics.rs	0.0% <0.0%> (ø)
opentelemetry-otlp/src/exporter/http/mod.rs	0.0% <0.0%> (ø)
... and 16 more

... and 1 file with indirect coverage changes

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[TommyCpp]

Maybe need to add CHANGELOG but otherwise LGTM Thanks!

[shaun-cox]

Will be updating CHANGELOG.md's, then readying this for review/approval...

[djc]

Thanks for taking care of this.