xds: return all ServerConfig dial options together

[eshitachandwani]

Fixes : #7661

Added a single DialOptions() method that returns a slice of all dial options for the type ServerConfig instead of individual methods to get all dial options.

RELEASE NOTES: None

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.82%. Comparing base (7aee163) to head (7d3bc83).
Report is 15 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7680      +/-   ##
==========================================
- Coverage   82.00%   81.82%   -0.18%     
==========================================
  Files         361      361              
  Lines       27825    27820       -5     
==========================================
- Hits        22817    22763      -54     
- Misses       3825     3857      +32     
- Partials     1183     1200      +17     

Files with missing lines	Coverage Δ
internal/xds/bootstrap/bootstrap.go	71.56% <100.00%> (+0.08%)	⬆️
xds/internal/xdsclient/transport/transport.go	94.02% <100.00%> (-0.08%)	⬇️

... and 30 files with indirect coverage changes

[easwars]

Also, there is a typo in the PR title and we don't need release notes for this change. This is a completely internal API and does not make sense to our users.